Jupiter's north polar region is coming into view as NASA's Juno spacecraft approaches the giant planet. This view of Jupiter was taken on August 27, when Juno was 437,000 miles (703,000 kilometers) away. Credits: NASA/JPL-Caltech/SwRI/MSSS
Jupiter’s north polar region is coming into view as NASA’s Juno spacecraft approaches the giant planet. This view of Jupiter was taken on August 27, when Juno was 437,000 miles (703,000 kilometers) away. Credits: NASA/JPL-Caltech/SwRI/MSSS
Saturdays’ close encounter with Jupiter soaring over its north pole was the first of 36 planned orbital flyby’s by Juno during the scheduled 20 month long prime mission.
“Soarin’ over #Jupiter. My 1st up-close look of the gas-giant world was a success!” the probe tweeted today post-flyby.
NASA released Juno’s first up-close image taken by the JunoCam visible light camera just hours later – as seen above.
Juno was speeding at some 130,000 mph (208,000 kilometers per hour) during the time of Saturday’s closest approach at 9:44 a.m. EDT (6:44 a.m. PDT 13:44 UTC) over the north polar region.
It passed merely 2,600 miles (4,200 kilometers) above the turbulent clouds of the biggest planet in our solar system during its initial 53.5 day polar elliptical capture orbit.
And apparently everything proceeded as the science and engineering team leading the mission to the gas giant had planned.
“Early post-flyby telemetry indicates that everything worked as planned and Juno is firing on all cylinders,” said Rick Nybakken, Juno project manager at NASA’s Jet Propulsion Laboratory in Pasadena, California, in a statement.
This dual view of Jupiter was taken on August 23, when NASA’s Juno spacecraft was 2.8 million miles (4.4 million kilometers) from the gas giant planet on the inbound leg of its initial 53.5-day capture orbit. Credit: NASA/JPL-Caltech/SwRI/MSSS
Indeed Saturday’s encounter will count as the closest of the entire prime mission. It also marks the first time that the entire suite of nine state-of-the-art science instruments had been turned on to gather the totally unique observations of Jupiter’s interior and exterior environment.
“We are getting some intriguing early data returns as we speak,” said Scott Bolton, principal investigator of Juno from the Southwest Research Institute in San Antonio, in a statement.
“This is our first opportunity to really take a close-up look at the king of our solar system and begin to figure out how he works.”
Additional up-close high resolution imagery of the Jovian atmosphere, swirling cloud tops and north and south poles snapped by JunoCam will be released in the coming weeks, perhaps as soon as next week.
“We are in an orbit nobody has ever been in before, and these images give us a whole new perspective on this gas-giant world,” said Bolton.
“It will take days for all the science data collected during the flyby to be downlinked and even more to begin to comprehend what Juno and Jupiter are trying to tell us.”
The prime mission is scheduled to end in February of 2018 with a suicide plunge into the Jovian atmosphere to prevent any possible contamination with Jupiter’s potentially habitable moons such as Europa and Ganymede.
“No other spacecraft has ever orbited Jupiter this closely, or over the poles in this fashion,” said Steve Levin, Juno project scientist from NASA’s Jet Propulsion Laboratory in Pasadena, California. “This is our first opportunity and there are bound to be surprises. We need to take our time to make sure our conclusions are correct.”
The team did release an approach image taken by JunoCam on Aug. 23 when the spacecraft was 2.8 million miles (4.4 million kilometers) from the gas giant planet on the inbound leg of its initial 53.5-day capture orbit.
One additional long period orbit is planned. The main engine will fire again in October to reduce the orbit to the 14 day science orbit.
Animation of Juno 14-day orbits starting in late 2016. Credits: NASA/JPL-Caltech
The solar powered probe will collect unparalleled new data that will unveil the hidden inner secrets of Jupiter’s origin and evolution as it peers “beneath the obscuring cloud cover of Jupiter and study its auroras to learn more about the planet’s origins, structure, atmosphere and magnetosphere.”
The Juno spacecraft was built by prime contractor Lockheed Martin in Denver.
Illustration of NASA’s Juno spacecraft firing its main engine to slow down and go into orbit around Jupiter. Lockheed Martin built the Juno spacecraft for NASA’s Jet Propulsion Laboratory. Credit: NASA/Lockheed Martin
The last NASA spacecraft to orbit Jupiter was Galileo in 1995. It explored the Jovian system until 2003.
In the final weeks of the approach before Jupiter Orbit Insertion (JOI), JunoCam captured dramatic views of Jupiter and all four of the Galilean Moons moons — Io, Europa, Ganymede and Callisto.
At the post JOI briefing at JPL on July 5, these were combined into a spectacular JunoCam time-lapse movie released by Bolton and NASA.
Watch and be mesmerized -“for humanity, our first real glimpse of celestial harmonic motion” says Bolton.
Video caption: NASA’s Juno spacecraft captured a unique time-lapse movie of the Galilean satellites in motion about Jupiter. The movie begins on June 12th with Juno 10 million miles from Jupiter, and ends on June 29th, 3 million miles distant. The innermost moon is volcanic Io; next in line is the ice-crusted ocean world Europa, followed by massive Ganymede, and finally, heavily cratered Callisto. Galileo observed these moons to change position with respect to Jupiter over the course of a few nights. From this observation he realized that the moons were orbiting mighty Jupiter, a truth that forever changed humanity’s understanding of our place in the cosmos. Earth was not the center of the Universe. For the first time in history, we look upon these moons as they orbit Jupiter and share in Galileo’s revelation. This is the motion of nature’s harmony. Credits: NASA/JPL-Caltech/MSSS
Stay tuned here for Ken’s continuing Earth and Planetary science and human spaceflight news.
United Launch Alliance Atlas V liftoff with NASA’s Juno to Jupiter orbiter on Aug. 5, 2011 from Cape Canaveral Air Force Station, Florida. Credit: Ken Kremer/kenkremer.com
Illustration of NASA's Juno spacecraft firing its main engine to slow down and go into orbit around Jupiter. Lockheed Martin built the Juno spacecraft for NASA's Jet Propulsion Laboratory. Credit: NASA/Lockheed Martin
The Juno spacecraft made history on July 4th, 2016, when it became the second spacecraft in history to achieve orbit around Jupiter for the sake of a long-term mission. Following in the footsteps of the Galileo mission, the probe will spend the next 20 months gathering data on Jupiter’s atmosphere, clouds, interior and gravitational and magnetic fields, before purposefully crashing into the planet.
And on Saturday, August 27th, Juno will be making history once again. According to NASA, at precisely 12:51 UTC (5:51 a.m. PDT, 8:51 a.m. EDT) the spacecraft will be passing closer to the cloud tops of Jupiter than at any point in its main mission. And while the probe is expected to make 35 more close flybys of the gas giant before its mission ends in February of 2018, this particular one is expected to be especially revealing.
For one, it will be the first time that the probe has all of its scientific instruments online and surveying Jupiter’s atmosphere as it swings past. And during the flyby, the probe will be passing Jupiter’s cloud tops at a distance of 4,200 kilometers (2,500 miles) – closer than it will ever get again – while traveling at a speed of 208,000 km/hour (130,000 mph).
This annotated color view of Jupiter and its four largest moons — Io, Europa, Ganymede and Callisto — was taken by the JunoCam camera on NASA’s Juno spacecraft on June 21, 2016, at a distance of 6.8 million miles (10.9 million kilometers) from Jupiter. Image credit: NASA/JPL-Caltech/MSSS
This will not only be the closest approach to Jupiter made by any probe, but it will pass over Jupiter’s poles, which will give Juno the opportunity to get a look at some never-before-seen things. These will include infrared and microwave readings taken by Juno’s suite of eight instruments, but also some choice photographs.
Yes, in addition to its sensor package, Juno‘s visible light imager (aka. JunoCam) will also be active and taking some close-up pictures of the atmosphere and poles. While the scientific information is expected to keep NASA scientists occupied for some time to come, the JunoCam images are expected to be released later next week.
According to NASA, these images will be the highest resolution photos of the Jovian atmosphere ever taken, not to mention the first glimpse of Jupiter’s north and south poles ever. As Scott Bolton, principal investigator of Juno from the Southwest Research Institute in San Antonio, said in a NASA press release:
“This is the first time we will be close to Jupiter since we entered orbit on July 4. Back then we turned all our instruments off to focus on the rocket burn to get Juno into orbit around Jupiter. Since then, we have checked Juno from stem to stern and back again. We still have more testing to do, but we are confident that everything is working great, so for this upcoming flyby Juno’s eyes and ears, our science instruments, will all be open… This is our first opportunity to really take a close-up look at the king of our Solar System and begin to figure out how he works.”
NASA’s Juno spacecraft launched on August 6, 2011 and should arrive at Jupiter on July 4, 2016. Credit: NASA / JPL
Ever since the Juno spacecraft launched on Aug. 5th, 2011, from Cape Canaveral, Florida, scientists and astronomers have been waiting for the day when it would start sending back information on the Solar System’s greatest planet. By examining the atmosphere, interior, and magnetic environment of the gas giant, scientists hope to be able to answer burning questions about the history of the planet’s formation.
For example, Jupiter’s interior structure and composition, as well as what drives its magnetic field, are still the subject of debate. In addition, there are some unanswered questions about when and where the planet formed. While it may have formed in its current orbit, some evidence suggests that it could have formed farther from the sun before migrating inward. All of these questions, it is hoped, are things the Juno mission will answer.
In so doing, scientists hope to be able to shed some additional light on the history of the Solar System as well. Like the other gas giants, it was assembled during the early phases, before our Sun had the chance to absorb or blow away the light gases in the huge cloud from which both were born. As such, Jupiter’s composition could tell us much about the early Solar System.
And this Saturday, the probe will be gathering what could prove to be the most crucial information its mission will produce. And of course, if all goes well, it will be taking the most detailed pictures of the Jovian giant to date! Godspeed, little Juno. You be careful out there!
Two planets close and up close. This is the view through a telescope during the extremely close conjunction of Jupiter and Venus on August 27. Credit: Stellarium
Saturn, Mars and Antares are shown on Sunday night August 21 two nights before their lineup. Mars is still the brightest of the bunch at magnitude –0.5. It will with Saturn at +0.4 and Antares at +1.0. Details: 35mm lens, f/2.8, ISO 400, 10 seconds. Credit: Bob King
Conjunctions of bright planets make for jewelry in the sky. This week, get ready for some celestial shimmer. If you’ve been following the hither and thither of Mars and Saturn near Antares this summer, you know these planets have been constantly on the move, creating all kinds of cool alignments in the southern sky.
On Tuesday night (August 23) the hopscotching duo will fall in line atop Antares in the southwestern sky at nightfall. Mars will sit just 1.5° above the star and Saturn 4° above Mars. Viewed from the Americas and Europe, the line will appear slightly bent. To catch them perfectly lined up, you’ll have to be in central Asia on the following evening, but the view should be pleasing no matter where you live.
This will be the scene facing southwest at nightfall from the central U.S. on Tuesday night August 23. The two planets and star form a compact gathering that’s sure to grab your attention. The moment of conjunction between Mars and Saturn occurs at 11:00 UT (7 a.m. Eastern Aug. 24), but they’ll be below the horizon at that time for the Americas and Europe. Credit: Stellarium
Nice as it is, the Mars-Saturn-Antares lineup is only the warm-up for the big event: the closest conjunction of the two brightest planets this year. On Saturday evening, August 27, Venus and Jupiter will approach within a hair’s breadth of each other as viewed with the naked eye — only 0.1° will separate the two gems. That’s one-fifth of a full moon’s width! While Mars and Saturn will be a snap to spot low in the southwestern sky during their conjunction, Venus and Jupiter snuggle near the western horizon at dusk.
Look for Venus and Jupiter right next to each other 4° (about three fingers held together horizontally) above the western horizon about a half-hour after sunset on August 27. This map shows the view from across the central U.S. at about 40°N latitude. The two planets will be closest at 22:00 UT (6 p.m. Eastern, 7 p.m. Central, 8 p.m. Mountain and 9 p.m. Pacific). Map: Bob King; source: Stellarium
To make sure you see them, find a place in advance of the date with a wide open view to the west. I also suggest bringing a pair of binoculars. It’s so much easier to find an object in bright twilight with help from the glass. You can start looking about 25 minutes after sunset; Venus will catch your eye first. Once you’ve found it, look a smidge to its lower right for Jupiter. If you’re using binoculars, lower them to see how remarkably close the two planets appear using nothing but your eyeballs. Perhaps they’ll remind you of a bright double star in a telescope or even the twin suns of Tatooine in Star Wars.
The two planets will be only 6 arc minutes apart Saturday evening and easily fit in the same field of view of a telescope at high magnification. Jupiter’s four brightest moons will be obvious. If you’re patient and wait for the air to settle, you’ll be able to make out Venus’s waxing gibbous phase. Credit: Stellarium
Have a small telescope? Take it along — Jupiter and Venus are so close together that they easily fit in the same high magnification field of view. Jupiter’s four brightest moons will be on display, and Venus will look just like a miniature version of the waxing gibbous moon. Rarely do the sky’s two brightest planets nearly fuse, making this a not-to-miss event.
Venus and Jupiter do a little square dance over the nights of August 26-28. Jupiter is headed westward toward conjunction with the sun, while Venus is moving away from the sun in the opposite direction from our perspective. Credit: Stellarium
If cloudy weather’s in the forecast that night, you can still spot them relatively close together the night before and night after, when they’ll be about 1° or two full moon diameters apart. I get pretty jazzed when bright objects approach closely in the sky, and I’m betting you do, too.
I also don’t mind being taken in by illusion once in a while. During a conjunction, planets only appear close together because we view them along the same line of sight. Their real distances add a dose of reality.
On Saturday evening Venus will be 143 million miles (230 million km) away vs. 592 million miles (953 million km) for Jupiter. In spite of appearing to almost touch, Jupiter is more than four times farther than the goddess planet.
The showpieces in this week’s conjunction parade: Jupiter, Venus, Mars and Saturn. Credit: NASA/ESA
That distance translates to the chill realm of the giant gaseous planets where sunlight is weak and ice is common. Try stretching your imagination that evening to sense as best you can the vast gulf between the two worlds.
You might also try taking a picture of them with your mobile phone. I suggest this because the sky will be light enough to get a hand-held photo of the scene. Photos or not, don’t miss what the planets have in store for earthlings this week.
An artist's concept of the Europa mission. The multi-year mission would conduct fly-bys of Europa designed to protect it from the extreme environment there. Image: NASA/JPL-Caltech
Jupiter’s moon Europa is a juicy target for exploration. Beneath its surface of ice there’s a warm salty, ocean. Or potentially, at least. And if Earth is our guide, wherever you find a warm, salty, ocean, you find life. But finding it requires a dedicated, and unique, mission.
If each of the bodies in our Solar System weren’t so different from each other, we could just have one or two types of missions. Things would be much easier, but also much more boring. But Europa isn’t boring, and it won’t be easy to explore. Exploring it will require a complex, custom mission. That means expensive.
NASA’s proposed mission to Europa is called the Europa Clipper. It’s been in the works for a few years now. But as the mission takes shape, and as the science gets worked out, a parallel process of budget wrangling is also ongoing. And as reported by SpaceNews.com there could be bad news incoming for the first-ever mission to Europa.
Images from NASA’s Galileo spacecraft show the intricate detail of Europa’s icy surface. Image: NASA/JPL-Caltech/ SETI Institute
At issue is next year’s funding for the Europa Clipper. Officials with NASA’s Outer Planets Assessment Group are looking for ways to economize and cut costs for Fiscal Year (FY) 2017, while still staying on track for a mission launch in 2022.
According to Bob Pappalardo, Europa Clipper’s project scientist at the Jet Propulsion Laboratory, funding will be squeezed in 2017. “There is this squeeze in FY17 that we have,” said Pappalardo. “We’re asking the instrument teams and various other aspects of the project, given that squeeze, what will it take in the out years to maintain that ’22 launch.”
As for the actual dollar amounts, there are different numbers floating around, and they don’t all jive with each other. In 2016, the Europa Mission received $175 million from Congress, but in the administration’s budget proposal for 2017, they only requested $49.6 million.
There’s clearly some uncertainty in these numbers, and that uncertainty is reflected in Congress, too. An FY 2017 House bill earmarks $260 million for the Europa mission. And the Senate has crafted a bill in support of the mission, but doesn’t allocate any funding for it. Neither the Senate nor the Congress has passed their bills.
This is not the first time that a mis-alignment has appeared between NASA and the different levels of government when it comes to funding. It’s pretty common. It’s also pretty common for the higher level of funding to prevail. But it’s odd that NASA’s requested amount is so low. NASA’s own low figure of $49.6 million is fuelling the perception that they themselves are losing interest in the Europa Clipper.
But SpaceNews.com is reporting that that is not the case. According to Curt Niebur, NASA’s program scientist for the Europa mission, “Everyone is aware of how supportive and generous Congress has been of this mission, and I’m happy to say that that support and encouragement is now shared by the administration, and by NASA as well. Everybody is on board the Europa Clipper and getting this mission to the launch pad as soon as our technical challenges and our budget will allow.”
What all this seems to mean is that the initial science and instrumentation for the mission will be maintained, but no additional capacity will be added. NASA is no longer considering things like free-flying probes to measure the plumes of water ice coming off the moon. According to Niebur, “The additional science value provided by these additions was not commensurate with the associated impact to resources, to accommodation, to cost. There just wasn’t enough science there to balance that out.”
The Europa Clipper will be a direct shot to Europa, without any gravity assist on the way. It will likely be powered by the Space Launch System. The main goal of the mission is to learn more about the icy moon’s potential habitability. There are tantalizing clues that it has an ocean about 100 km thick, kept warm by the gravity-tidal interactions with Jupiter, and possibly by radioactive decay in the rocky mantle. There’s also some evidence that the composition of the sub-surface ocean is similar to Earth’s.
Mars is a fascinating target, no doubt about it. But as far as harbouring life, Europa might be a better bet. Europa’s warm, salty ocean versus Mar’s dry, cold surface? A lot of resources have been spent studying Mars, and the Europa mission represents a shift in resources in that regard.
It’s unfortunate that a few tens of million dollars here or there can hamper our search for life beyond Earth. But the USA is a democracy, so that’s the way it is. These discrepancies and possible disputes between NASA and the different levels of government may seem disconcerting, but that’s the way these things get done.
An illustration showing the 8 planets of the Solar System to scale Credit: NASA
At one time, humans believed that the Earth was the center of the Universe; that the Sun, Moon, planets and stars all revolved around us. It was only after centuries of ongoing observations and improved instrumentation that astronomers came to understand that we are in fact part a larger system of planets that revolve around the Sun. And it has only been within the last century that we’ve come to understand just how big our Solar System is.
And even now, we are still learning. In the past few decades, the total number of celestial bodies and moons that are known to orbit the Sun has expanded. We have also come to debate the definition of “planet” (a controversial topic indeed!) and introduced additional classifications – like dwarf planet, minor planet, plutoid, etc. – to account for new finds. So just how many planets are there and what is special about them? Let’s run through them one by one, shall we?
Mercury:
As you travel outward from the Sun, Mercury is the closest planet. It orbits the Sun at an average distance of 58 million km (36 million mi). Mercury is airless, and so without any significant atmosphere to hold in the heat, it has dramatic temperature differences. The side that faces the Sun experiences temperatures as high as 420 °C (788 °F), and then the side in shadow goes down to -173 °C (-279.4 °F).
MESSENGER image of Mercury from its third flyby. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
Like Venus, Earth and Mars, Mercury is a terrestrial planet, which means it is composed largely of refractory minerals such as the silicates and metals such as iron and nickel. These elements are also differentiated between a metallic core and a silicate mantle and crust, with Mercury possessing a larger-than-average core. Multiple theories have been proposed to explain this, the most widely accepted being that the impact from a planetesimal in the past blew off much of its mantle material.
Mercury is the smallest planet in the Solar System, measuring just 4879 km across at its equator. However, it is second densest planet in the Solar System, with a density of 5.427 g/cm3 – which is the second only to Earth. Because of this, Mercury experiences a gravitational pull that is roughly 38% that of Earth’s (0.38 g).
Mercury also has the most eccentric orbit of any planet in the Solar System (0.205), which means its distance from the Sun ranges from 46 to 70 million km (29-43 million mi). The planet also takes 87.969 Earth days to complete an orbit. But with an average orbital speed of 47.362 km/s, Mercury also takes 58.646 days to complete a single rotation.
Combined with its eccentric orbit, this means that it takes 176 Earth days for the Sun to return to the same place in the sky (i.e. a solar day) on Mercury, which is twice as long as a single Hermian year. Mercury also has the lowest axial tilt of any planet in the Solar System – approximately 0.027 degrees – compared to Jupiter’s 3.1 degrees, which is the second smallest.
The MESSENGER spacecraft has been in orbit around Mercury since March 2011 – but its days are numbered. Credit: NASA/JHUAPL/Carnegie Institution of Washington
Mercury has only been visited two times by spacecraft, the first being the Mariner 10 probe, which conducted a flyby of the planet back in the mid-1970s. It wasn’t until 2008 that another spacecraft from Earth made a close flyby of Mercury (the MESSENGER probe) which took new images of its surface, shed light on its geological history, and confirmed the presence of water ice and organic molecules in its northern polar region.
In summary, Mercury is made special by the fact it is small, eccentric, and varies between extremes of hot and cold. It’s also very mineral rich, and quite dense!
Venus:
Venus is the second planet in the Solar System, and is Earth’s virtual twin in terms of size and mass. With a mass of 4.8676×1024 kg and a mean radius of about 6,052 km, it is approximately 81.5% as massive as Earth and 95% as large. Like Earth (and Mercury and Mars), it is a terrestrial planet, composed of rocks and minerals that are differentiated.
But apart from these similarities, Venus is very different from Earth. Its atmosphere is composed primarily of carbon dioxide (96%), along with nitrogen and a few other gases. This dense cloud cloaks the planet, making surface observation very difficult, and helps heat it up to 460 °C (860 °F). The atmospheric pressure is also 92 times that of Earth’s atmosphere, and poisonous clouds of carbon dioxide and sulfuric acid rain are commonplace.
Venus’ similarity in size and mass has led to it being called “Earth’s sister planet’. Credit: NASA/JPL/Magellan
Venus orbits the Sun at an average distance of about 0.72 AU (108 million km; 67 million mi) with almost no eccentricity. In fact, with its farthest orbit (aphelion) of 0.728 AU (108,939,000 km) and closest orbit (perihelion) of 0.718 AU (107,477,000 km), it has the most circular orbit of any planet in the Solar System. The planet completes an orbit around the Sun every 224.65 days, meaning that a year on Venus is 61.5% as long as a year on Earth.
When Venus lies between Earth and the Sun, a position known as inferior conjunction, it makes the closest approach to Earth of any planet, at an average distance of 41 million km. This takes place, on average, once every 584 days, and is the reason why Venus is the closest planet to Earth. The planet completes an orbit around the Sun every 224.65 days, meaning that a year on Venus is 61.5% as long as a year on Earth.
Unlike most other planets in the Solar System, which rotate on their axes in an counter-clockwise direction, Venus rotates clockwise (called “retrograde” rotation). It also rotates very slowly, taking 243 Earth days to complete a single rotation. This is not only the slowest rotation period of any planet, it also means that a single day on Venus lasts longer than a Venusian year.
Venus’ atmosphere is also known to experience lightning storms. Since Venus does not experience rainfall (except in the form of sulfuric acid), it has been theorized that the lightning is being caused by volcanic eruptions. Several spacecraft have visited Venus, and a few landers have even made it to the surface to send back images of its hellish landscape. Even though there were made of metal, these landers only survived a few hours at best.
Venus is made special by the fact that it is very much like Earth, but also radically different. It’s thick atmosphere could crush a living being, its heat could melt lead, and its acid rain could dissolve flesh, bone and metal alike! It also rotates very slowly, and backwards relative to the other plants.
Earth:
Earth is our home, and the third planet from the Sun. With a mean radius of 6371 km and a mass of 5.97×1024 kg, it is the fifth largest and fifth most-massive planet in the Solar System. And with a mean density of 5.514 g/cm³, it is the densest planet in the Solar System. Like Mercury, Venus and Mars, Earth is a terrestrial planet.
But unlike these other planets, Earth’s core is differentiated between a solid inner core and liquid outer core. The outer core also spins in the opposite direction as the planet, which is believed to create a dynamo effect that gives Earth its protective magnetosphere. Combined with a atmosphere that is neither too thin nor too thick, Earth is the only planet in the Solar System known to support life.
The Earth’s layers, showing the Inner and Outer Core, the Mantle, and Crust. Credit: discovermagazine.com
In terms of its orbit, Earth has a very minor eccentricity (approx. 0.0167) and ranges in its distance from the Sun between 147,095,000 km (0.983 AU) at perihelion to 151,930,000 km (1.015 AU) at aphelion. This works out to an average distance (aka. semi-major axis) of 149,598,261 km, which is the basis of a single Astronomical Unit (AU)
The Earth has an orbital period of 365.25 days, which is the equivalent of 1.000017 Julian years. This means that every four years (in what is known as a Leap Year), the Earth calendar must include an extra day. Though a single solar day on Earth is considered to be 24 hours long, our planet takes precisely 23h 56m and 4 s to complete a single sidereal rotation (0.997 Earth days).
Earth’s axis is also tilted 23.439281° away from the perpendicular of its orbital plane, which is responsible for producing seasonal variations on the planet’s surface with a period of one tropical year (365.24 solar days). In addition to producing variations in terms of temperature, this also results in variations in the amount of sunlight a hemisphere receives during the course of a year.
Earth has only a single moon: the Moon. Thanks to examinations of Moon rocks that were brought back to Earth by the Apollo missions, the predominant theory states that the Moon was created roughly 4.5 billion years ago from a collision between Earth and a Mars-sized object (known as Theia). This collision created a massive cloud of debris that began circling our planet, which eventually coalesced to form the Moon we see today.
A picture of Earth taken by Apollo 11 astronauts. Credit: NASA
What makes Earth special, you know, aside from the fact that it is our home and where we originated? It is the only planet in the Solar System where liquid, flowing water exists in abundance on its surface, has a viable atmosphere, and a protective magnetosphere. In other words, it is the only planet (or Solar body) that we know of where life can exist on the surface.
In addition, no planet in the Solar System has been studied as well as Earth, whether it be from the surface or from space. Thousands of spacecraft have been launched to study the planet, measuring its atmosphere, land masses, vegetation, water, and human impact. Our understanding of what makes our planet unique in our Solar System has helped in the search for Earth-like planets in other systems.
Mars:
The fourth planet from the Sun is Mars, which is also the second smallest planet in the Solar System. It has a radius of approximately 3,396 km at its equator, and 3,376 km at its polar regions – which is the equivalent of roughly 0.53 Earths. While it is roughly half the size of Earth, it’s mass – 6.4185 x 10²³ kg – is only 0.151 that of Earth’s. It’s density is also lower than Earths, which leads to it experiencing about 1/3rd Earth’s gravity (0.376 g).
It’s axial tilt is very similar to Earth’s, being inclined 25.19° to its orbital plane (Earth’s axial tilt is just over 23°), which means Mars also experiences seasons. Mars has almost no atmosphere to help trap heat from the Sun, and so temperatures can plunge to a low of -140 °C (-220 °F) in the Martian winter. However, at the height of summer, temperatures can get up to 20 °C (68 °F) during midday at the equator.
However, recent data obtained by the Curiosity rover and numerous orbiters have concluded that Mars once had a denser atmosphere. Its loss, according to data obtained by NASA’s Mars Atmosphere and Volatile Evolution (MAVEN), the atmosphere was stripped away by solar wind over the course of a 500 million year period, beginning 4.2 billion years ago.
At its greatest distance from the Sun (aphelion), Mars orbits at a distance of 1.666 AUs, or 249.2 million km. At perihelion, when it is closest to the Sun, it orbits at a distance of 1.3814 AUs, or 206.7 million km. At this distance, Mars takes 686.971 Earth days, the equivalent of 1.88 Earth years, to complete a rotation of the Sun. In Martian days (aka. Sols, which are equal to one day and 40 Earth minutes), a Martian year is 668.5991 Sols.
Like Mercury, Venus, and Earth, Mars is a terrestrial planet, composed mainly of silicate rock and metals that are differentiated between a core, mantle and crust. The red-orange appearance of the Martian surface is caused by iron oxide, more commonly known as hematite (or rust). The presence of other minerals in the surface dust allow for other common surface colors, including golden, brown, tan, green, and others.
Although liquid water cannot exist on Mars’ surface, owing to its thin atmosphere, large concentrations of ice water exist within the polar ice caps – Planum Boreum and Planum Australe. In addition, a permafrost mantle stretches from the pole to latitudes of about 60°, meaning that water exists beneath much of the Martian surface in the form of ice water. Radar data and soil samples have confirmed the presence of shallow subsurface water at the middle latitudes as well.
MSL Curiosity selfie on the surface of Mars. Image: NASA/JPL/Cal-Tech
Mars has two tiny asteroid-sized moons: Phobos and Deimos. Because of their size and shape, the predominant theory is that Mars acquired these two moons after they were kicked out of the Asteroid Belt by Jupiter’s gravity.
Mars has been heavily studied by spacecraft. There are multiple rovers and landers currently on the surface and a small fleet of orbiters flying overhead. Recent missions include the Curiosity Rover, which gathered ample evidence on Mars’ water past, and the groundbreaking discovery of finding organic molecules on the surface. Upcoming missions include NASA’s InSight lander and the Exomars rover.
Hence, Mars’ special nature lies in the fact that it also is terrestrial and lies within the outer edge of the Sun’s habitable zone. And whereas it is a cold, dry place today, it once had an thicker atmosphere and plentiful water on its surface.
Jupiter:
Mighty Jupiter is the fouth planet for our Sun and the biggest planet in our Solar System. Jupiter’s mass, volume, surface area and mean circumference are 1.8981 x 1027 kg, 1.43128 x 1015 km3, 6.1419 x 1010 km2, and 4.39264 x 105 km respectively. To put that in perspective, Jupiter diameter is roughly 11 times that of Earth, and 2.5 times the mass of all the other planets in the Solar System combined.
Jupiter has spectacular aurora, such as this view captured by the Hubble Space Telescope. Credit: NASA, ESA, and J. Nichols (University of Leicester)
But, being a gas giant, it has a relatively low density – 1.326 g/cm3 – which is less than one quarter of Earth’s. This means that while Jupiter’s volume is equivalent to about 1,321 Earths, it is only 318 times as massive. The low density is one way scientists are able to determine that it is made mostly of gases, though the debate still rages on what exists at its core (see below).
Jupiter orbits the Sun at an average distance (semi-major axis) of 778,299,000 km (5.2 AU), ranging from 740,550,000 km (4.95 AU) at perihelion and 816,040,000 km (5.455 AU) at aphelion. At this distance, Jupiter takes 11.8618 Earth years to complete a single orbit of the Sun. In other words, a single Jovian year lasts the equivalent of 4,332.59 Earth days.
However, Jupiter’s rotation is the fastest of all the Solar System’s planets, completing a rotation on its axis in slightly less than ten hours (9 hours, 55 minutes and 30 seconds to be exact). Therefore, a single Jovian year lasts 10,475.8 Jovian solar days. This orbital period is two-fifths that of Saturn, which means that the two largest planets in our Solar System form a 5:2 orbital resonance.
Much like Earth, Jupiter experiences auroras near its northern and southern poles. But on Jupiter, the auroral activity is much more intense and rarely ever stops. The intense radiation, Jupiter’s magnetic field, and the abundance of material from Io’s volcanoes that react with Jupiter’s ionosphere create a light show that is truly spectacular.
The Juno spacecraft isn’t the first one to visit Jupiter. Galileo went there in the mid 90’s, and Voyager 1 snapped a nice picture of the clouds on its mission. Credit: NASA
Jupiter also experiences violent weather patterns. Wind speeds of 100 m/s (360 km/h) are common in zonal jets, and can reach as high as 620 kph (385 mph). Storms form within hours and can become thousands of km in diameter overnight. One storm, the Great Red Spot, has been raging since at least the late 1600s. The storm has been shrinking and expanding throughout its history; but in 2012, it was suggested that the Giant Red Spot might eventually disappear.
Jupiter is composed primarily of gaseous and liquid matter. It is the largest of the gas giants, and like them, is divided between a gaseous outer atmosphere and an interior that is made up of denser materials. It’s upper atmosphere is composed of about 88–92% hydrogen and 8–12% helium by percent volume of gas molecules, and approx. 75% hydrogen and 24% helium by mass, with the remaining one percent consisting of other elements.
The interior contains denser materials, such that the distribution is roughly 71% hydrogen, 24% helium and 5% other elements by mass. It is believed that Jupiter’s core is a dense mix of elements – a surrounding layer of liquid metallic hydrogen with some helium, and an outer layer predominantly of molecular hydrogen. The core has also been described as rocky, but this remains unknown as well.
Jupiter has been visited by several spacecraft, including NASA’s Pioneer 10 and Voyager spacecraft in 1973 and 1980, respectively; and by the Cassini and New Horizons spacecraft more recently. Until the recent arrival of Juno, only the Galileo spacecraft has ever gone into orbit around Jupiter, and it was crashed into the planet in 2003 to prevent it from contaminating one of Jupiter’s icy moons.
Illustration of Jupiter and the Galilean satellites. Credit: NASA
In short, Jupiter is massive and has massive storms. But compared to the planets of the inner Solar System, is it significantly less dense. Jupiter also has the most moons in the Solar System, with 67 confirmed and named moons orbiting it. But it is estimated that as many as 200 natural satellites may exist around the planet. Little wonder why this planet is named after the king of the gods.
Saturn:
Saturn is the second largest planet in the Solar System. With a mean radius of 58232±6 km, it is approximately 9.13 times the size of Earth. And at 5.6846×1026 kg, it is roughly 95.15 as massive. However, since it is a gas giant, it has significantly greater volume – 8.2713×1014 km3, which is equivalent to 763.59 Earths.
The sixth most distant planet, Saturn orbits the Sun at an average distance of 9 AU (1.4 billion km; 869.9 million miles). Due to its slight eccentricity, the perihelion and aphelion distances are 9.022 (1,353.6 million km; 841.3 million mi) and 10.053 AU (1,513,325,783 km; 940.13 million mi), on average respectively.
With an average orbital speed of 9.69 km/s, it takes Saturn 10,759 Earth days to complete a single revolution of the Sun. In other words, a single Cronian year is the equivalent of about 29.5 Earth years. However, as with Jupiter, Saturn’s visible features rotate at different rates depending on latitude, and multiple rotation periods have been assigned to various regions.
This portrait looking down on Saturn and its rings was created from images obtained by NASA’s Cassini spacecraft on Oct. 10th, 2013. Credit: NASA/JPL-Caltech/Space Science Institute/G. Ugarkovic
As a gas giant, Saturn is predominantly composed of hydrogen and helium gas. With a mean density of 0.687 g/cm3, Saturn is the only planet in the Solar System that is less dense than water; which means that it lacks a definite surface, but is believed to have a solid core. This is due to the fact that Saturn’s temperature, pressure, and density all rise steadily toward the core.
Standard planetary models suggest that the interior of Saturn is similar to that of Jupiter, having a small rocky core surrounded by hydrogen and helium with trace amounts of various volatiles. This core is similar in composition to the Earth, but more dense due to the presence of metallic hydrogen, which as a result of the extreme pressure.
As a gas giant, the outer atmosphere of Saturn contains 96.3% molecular hydrogen and 3.25% helium by volume. Trace amounts of ammonia, acetylene, ethane, propane, phosphine and methane have been also detected in Saturn’s atmosphere. Like Jupiter, it also has a banded appearance, but Saturn’s bands are much fainter and wider near the equator.
On occasion, Saturn’s atmosphere exhibits long-lived ovals that are thousands of km wide, similar to what is commonly observed on Jupiter. Whereas Jupiter has the Great Red Spot, Saturn periodically has what’s known as the Great White Spot (aka. Great White Oval). This unique but short-lived phenomenon occurs once every Saturnian year, roughly every 30 Earth years, around the time of the northern hemisphere’s summer solstice.
The huge storm churning through the atmosphere in Saturn’s northern hemisphere overtakes itself as it encircles the planet in this true-color view from NASA’s Cassini spacecraft. Image credit: NASA/JPL-Caltech/SSI
The persisting hexagonal wave pattern around the north pole was first noted in the Voyager images. The sides of the hexagon are each about 13,800 km (8,600 mi) long (which is longer than the diameter of the Earth) and the structure rotates with a period of 10h 39m 24s, which is assumed to be equal to the period of rotation of Saturn’s interior.
The south pole vortex, meanwhile, was first observed using the Hubble Space Telescope. These images indicated the presence of a jet stream, but not a hexagonal standing wave. These storms are estimated to be generating winds of 550 km/h, are comparable in size to Earth, and believed to have been going on for billions of years. In 2006, the Cassini space probe observed a hurricane-like storm that had a clearly defined eye. Such storms had not been observed on any planet other than Earth – even on Jupiter.
Of course, the most amazing feature of Saturn is its rings. These are made of particles of ice ranging in size from a grains of sand to the size of a car. Some scientists think the rings are only a few hundred million years old, while others think they could be as old as the Solar System itself.
Saturn has been visited by spacecraft 4 times: Pioneer 11, Voyager 1 and 2 were just flybys, but Cassini has actually gone into orbit around Saturn and has captured thousands of images of the planet and its moons. And speaking of moons, Saturn has a total of 62 moons discovered (so far), though estimates indicate that it might have as many as 150.
A collage of Saturn (bottom left) and some of its moons: Titan, Enceladus, Dione, Rhea and Helene. Credit: NASA/JPL/Space Science Institute
So like Jupiter, Saturn is a massive gas giant that experiences some very interesting weather patterns. It also has lots of moons and has a very low density. But what really makes Saturn stand out is its impressive ring system. Whereas every gas and ice giant has one, Saturn’s is visible to the naked eye and very beautiful to behold!
Uranus:
Next comes Uranus, the seventh planet from the Sun. With a mean radius of approximately 25,360 km and a mass of 8.68 × 1025 kg, Uranus is approximately 4 times the sizes of Earth and 63 times its volume. However, as a gas giant, its density (1.27 g/cm3) is significantly lower; hence, it is only 14.5 as massive as Earth.
The variation of Uranus’ distance from the Sun is also greater than that any other planet (not including dwarf planets or plutoids). Essentially, the gas giant’s distance from the Sun varies from 18.28 AU (2,735,118,100 km) at perihelion to 20.09 AU (3,006,224,700 km) at aphelion. At an average distance of 3 billion km from the Sun, it takes Uranus roughly 84 years (or 30,687 days) to complete a single orbit of the Sun.
The standard model of Uranus’s structure is that it consists of three layers: a rocky (silicate/iron–nickel) core in the center, an icy mantle in the middle and an outer envelope of gaseous hydrogen and helium. Much like Jupiter and Saturn, hydrogen and helium account for the majority of the atmosphere – approximately 83% and 15% – but only a small portion of the planet’s overall mass (0.5 to 1.5 Earth masses).
Uranus as seen through the automated eyes of Voyager 2 in 1986. (Credit: NASA/JPL)
The third most abundant element is methane ice (CH4), which accounts for 2.3% of its composition and which accounts for the planet’s aquamarine or cyan coloring. Trace amounts of various hydrocarbons are also found in the stratosphere of Uranus, which are thought to be produced from methane and ultraviolent radiation-induced photolysis. They include ethane (C2H6), acetylene (C2H2), methylacetylene (CH3C2H), and diacetylene (C2HC2H).
In addition, spectroscopy has uncovered carbon monoxide and carbon dioxide in Uranus’ upper atmosphere, as well as the presence icy clouds of water vapor and other volatiles, such as ammonia and hydrogen sulfide. Because of this, Uranus and Neptune are considered a distinct class of giant planet – known as “Ice Giants” – since they are composed mainly of heavier volatile substances.
The rotational period of the interior of Uranus is 17 hours, 14 minutes. As with all giant planets, its upper atmosphere experiences strong winds in the direction of rotation. Hence its weather systems are also broken up into bands that rotate around the planet, which are driven by internal heat rising to the upper atmosphere.
As a result, winds on Uranus can reach up to 900 km/h (560 mph), creating massive storms like the one spotted by the Hubble Space Telescope in 2012. Similar to Jupiter’s Great Red Spot, this “Dark Spot” was a giant cloud vortex that measured 1,700 kilometers by 3,000 kilometers (1,100 miles by 1,900 miles).
Huge storms on Uranus were spotted by the Keck Observatory on Aug. 5 and Aug. 6, 2014. Credit: Imke de Pater (UC Berkeley), Pat Fry (University of Wisconsin), Keck Observatory
One unique feature of Uranus is that it rotates on its side. Whereas all of the Solar System’s planets are tilted on their axes to some degree, Uranus has the most extreme axial tilt of 98°. This leads to the radical seasons that the planet experiences, not to mention an unusual day-night cycle at the poles. At the equator, Uranus experiences normal days and nights; but at the poles, each experience 42 Earth years of day followed by 42 years of night.
Uranus was the first planet to be discovered with a telescope; it was first recognized as a planet in 1781 by William Herschel. Beyond Earth-based observations, only one spacecraft (Voyager 2) has ever studied Uranus up close. It passed by the planet in 1986, and captured the first close images. Uranus has 27 known moons.
Uranus’ special nature comes through in its natural beauty, its intense weather, its ring system and its impressive array of moons. And it’s compositions, being an “ice” giant, is what gives its aquamarine color. But perhaps mist interesting is its sideways rotation, which is unique among the Solar planets.
Neptune:
Neptune is the 8th and final planet in the Solar System, orbiting the Sun at a distance of 29.81 AU (4.459 x 109 km) at perihelion and 30.33 AU (4.537 x 109 km) at aphelion. With a mean radius of 24,622 ± 19 km, Neptune is the fourth largest planet in the Solar System and four times as large as Earth. But with a mass of 1.0243×1026 kg – which is roughly 17 times that of Earth – it is the third most massive, outranking Uranus.
Neptune’s system of moons and rings visualized. Credit: SETI
Neptune takes 16 h 6 min 36 s (0.6713 days) to complete a single sidereal rotation, and 164.8 Earth years to complete a single orbit around the Sun. This means that a single day lasts 67% as long on Neptune, whereas a year is the equivalent of approximately 60,190 Earth days (or 89,666 Neptunian days).
Due to its smaller size and higher concentrations of volatiles relative to Jupiter and Saturn, Neptune (much like Uranus) is often referred to as an “ice giant” – a subclass of a giant planet. Also like Uranus, Neptune’s internal structure is differentiated between a rocky core consisting of silicates and metals; a mantle consisting of water, ammonia and methane ices; and an atmosphere consisting of hydrogen, helium and methane gas.
The core of Neptune is composed of iron, nickel and silicates, with an interior model giving it a mass about 1.2 times that of Earth. The pressure at the center is estimated to be 7 Mbar (700 GPa), about twice as high as that at the center of Earth, and with temperatures as high as 5,400 K. At a depth of 7000 km, the conditions may be such that methane decomposes into diamond crystals that rain downwards like hailstones.
Because Neptune’s axial tilt (28.32°) is similar to that of Earth (~23°) and Mars (~25°), the planet experiences similar seasonal changes. Combined with its long orbital period, this means that the seasons last for forty Earth years. Also owing to its axial tilt being comparable to Earth’s is the fact that the variation in the length of its day over the course of the year is not any more extreme than it on Earth.
Reconstruction of Voyager 2 images showing the Great Black spot (top left), Scooter (middle), and the Small Black Spot (lower right). Credit: NASA/JPL
Just like Jupiter and Saturn, Neptune has bands of storms that circle the planet. Astronomers have clocked winds on Neptune traveling at 2,100 km/hour, which is believed to be due to Neptune’s cold temperatures – which may decrease the friction in the system, During its 1989 flyby, NASA’s Voyager 2 spacecraft discovered the Great Dark Spot on Neptune.
Similar to Jupiter’s Great Red Spot, this is an anti-cyclonic storm measuring 13,000 km x 6,600 km across. A few years later, however, the Hubble Space Telescope failed to see the Great Dark Spot, but it did see different storms. This might mean that storms on Neptune don’t last as long as they do on Jupiter or even Saturn.
The more active weather on Neptune might be due, in part, to its higher internal heat. Although Neptune is much more distant than Uranus from the Sun, receiving 40% less sunlight, temperatures on the surface of the two planets are roughly similar. In fact, Neptune radiates 2.61 times as much energy as it receives from the Sun. This is enough heat to help drive the fastest winds in the Solar System.
Neptune is the second planet discovered in modern times. It was discovered at the same time by both Urbain Le Verrier and John Couch Adams. Neptune has only ever been visited by one spacecraft, Voyager 2, which made a fly by in August, 1989. Neptune has 13 known moons. Th largest and most famous of these is Triton, which is believed to be a former KBO that was captured by Neptune’s gravity.
Global Color Mosaic of Triton, taken by Voyager 2 in 1989. Credit: NASA/JPL/USGS
So much like Uranus, Neptune has a ring system, some intense weather patterns, and an impressive array of moons. Also like Uranus, Neptune’s composition allows for its aquamarine color; except that in Neptune’s case, this color is more intense and vivid. In addition, Neptune experiences some temperature anomalies that are yet to be explained. And let’s not forgt the raining diamonds!
And those are the planets in the Solar System thank you for joining the tour! Unfortunately, Pluto isn’t a planet any more, hence why it was not listed. We know, we know, take it up with the IAU!
When we used to do the Virtual Star Party (and I really need to start those up again, they were super fun), I had the worst luck with Jupiter’s Great Red Spot. Whenever Jupiter was in the sky, the Great Red Spot always eluded us. Even though we should have had a 50/50 shot at seeing the massive storm on Jupiter, it was always hiding. Why so shy Jovian storm?
Jupiter’s Great Red Spot is an enormous swirling storm located on a band of clouds just south of the planet’s equator. It’s been there as long as people have been observing Jupiter with good enough telescopes to resolve it.
Astronomers somewhat disagree exactly when that was. The first person to mention a spot on Jupiter was Robert Hooke, who described it in 1664, but he placed it in the northern hemisphere. Oops.
A more reliable account comes from Giovanni Cassini, best known for his observations of Saturn. He observed a permanent spot in roughly the same location from 1665 to 1713.
Drawings by Cassini of what is presumably the Great Red Spot in 1665
The strange part is that astronomers lost track of it until 1830, when the modern Spot we know today was clearly evident. Were they two different spots? Did the GRS disappear and the flare up again? We’ll never know.
But really, isn’t that just splitting hairs? The thought that there’s been an enormous Jovian hurricane swirling away for hundreds of years is awesome and terrifying.
Here on Earth, we classify hurricanes as Category 1 when the wind speed crosses 119 km/h. A Category 4 hurricane can hit more than 250 km/h. That’s scary fast wind speed that can tear apart buildings. The Great Red Spot, on the other hand, can reach almost 650 km/h.
How big is this thing, anyway? Trust me, it’s big, but it used to be bigger. When astronomers first started keeping accurate measurements in the late 1800s, the Great Red Spot was about 40,000 kilometers wide and 14,000 kilometers tall.
Since that time, it’s been steadily shrinking. When the Voyager spacecraft flew past in the late 1970s, the spot had shrunk to 23,000 kilometers across. In 1995 Hubble measured it as 21,000 kilometers across, and then again in 2009, it was 18,000 kilometers across. About a year ago, Hubble did another measurement, and now it’s only 16,500 kilometers wide.
I say “only”, but keep in mind that the Earth measures 12,742 kilometers across. In other words, the Great Red Spot could still swallow up an Earth with room to spare.
The Juno spacecraft isn’t the first one to visit Jupiter. Galileo went there in the mid 90’s, and Voyager 1 snapped a nice picture of the clouds on its mission. Image: NASA
But this shrinking is continuing by about 930 kilometers per year. And as it shrinks, it’s changing from an oval to a more circular shape. At the same time, the color is changing too, lightening up – perhaps because the storm doesn’t dig too deeply into the lower atmospheric layers.
It’s possible that the Great Red Spot could completely disappear within our generation. And then every astronomer would fail to be able to see the Spot, just like me.
The Great Red Spot isn’t the only long lived storm on Jupiter, and this could be the reason why the Spot is disappearing.
If you look at images of Jupiter from Hubble, you can see other cyclonic storms; the biggest of which is known as Oval BA. It was first observed in 2000, after a few smaller storms collided and merged into a little red spot.
The formation of Oval BA. Credit: NASA/JPL/WFPC2
Over time, Oval BA has been getting larger and stronger, now it’s about the size of the Earth, and wind speeds have reached more than 600 km/h rivalling the Great Red Spot.
Because the bands on Jupiter alternate in directions, astronomers think that storms on the nearby bands are sapping the strength of the Great Red Spot. And perhaps they’re boosting Oval BA. There might be a time when the two spots are roughly the same size. And when the Great Red Spot finally disappears, Oval BA will be there to assume the mantle.
Since these storms can clearly grow and shrink over hundreds of years, I wonder what some of the strangest configurations of storms have ever been. I guess future robot-body Fraser will be the one to find out.
Good news! At the time that you’re watching this, NASA’s Juno spacecraft arrived at Jupiter on July 4, 2016. For the first time in more than a decade, we have a dedicated spacecraft at Jupiter, mapping, probing and analyzing the giant planet.
We should be getting more close up measurements and observations of the Great Red Spot and everything Jovian, so stay tuned, it’s going to be exciting.
This color view from NASA's Juno spacecraft is made from some of the first images taken by JunoCam after the spacecraft entered orbit around Jupiter on July 4, 2016. Credits: NASA/JPL-Caltech/SwRI/MSSS
This color view from NASA’s Juno spacecraft is made from some of the first images taken by JunoCam after the spacecraft entered orbit around Jupiter on July 4, 2016. Credits: NASA/JPL-Caltech/SwRI/MSSS
NASA’s newly arrived Jovian orbiter Juno has transmitted its first imagery since reaching orbit last week on July 4 after swooping over Jupiter’s cloud tops and powering back up its package of state-of-the-art science instruments for unprecedented research into determining the origin of our solar systems biggest planet.
The ‘Galilean’ moons are annotated from left to right in the lead image.
Juno’s visible-light camera named JunoCam was turned on six days after Juno fired its main engine to slow down and be captured into orbit around Jupiter – the ‘King of the Planets’ following a nearly five year long interplanetary voyage from Earth.
The image was taken when Juno was 2.7 million miles (4.3 million kilometers) distant from Jupiter on July 10, at 10:30 a.m. PDT (1:30 p.m. EDT, 5:30 UTC), and traveling on the outbound leg of its initial 53.5-day capture orbit.
Juno came within only about 3000 miles of the cloud tops and passed through Jupiter’s extremely intense and hazardous radiation belts during orbital arrival over the north pole.
Illustration of NASA’s Juno spacecraft firing its main engine to slow down and go into orbit around Jupiter. Lockheed Martin built the Juno spacecraft for NASA’s Jet Propulsion Laboratory. Credit: NASA/Lockheed Martin
The newly released JunoCam image is visible proof that Juno survived the do-or-die orbital fireworks on America’s Independence Day that placed the baskeball-court sized probe into orbit around Jupiter – and is in excellent health to carry out its groundbreaking mission to elucidate Jupiter’s ‘Genesis.’
“This scene from JunoCam indicates it survived its first pass through Jupiter’s extreme radiation environment without any degradation and is ready to take on Jupiter,” said Scott Bolton, principal investigator from the Southwest Research Institute in San Antonio, in a statement.
“We can’t wait to see the first view of Jupiter’s poles.”
Within two days of the nerve wracking and fully automated 35-minute-long Jupiter Orbital Insertion (JOI) maneuver, the Juno engineering team begun powering up five of the probes science instruments on July 6.
Animation of Juno 14-day orbits starting in late 2016. Credits: NASA/JPL-Caltech
All nonessential instruments and systems had been powered down in the final days of Juno’s approach to Jupiter to ensure the maximum chances for success of the critical JOI engine firing.
“We had to turn all our beautiful instruments off to help ensure a successful Jupiter orbit insertion on July 4,” said Bolton.
“But next time around we will have our eyes and ears open. You can expect us to release some information about our findings around September 1.”
Juno resumed high data rate communications with Earth on July 5, the day after achieving orbit.
We can expect to see more JunoCam images taken during this first orbital path around the massive planet.
But the first high resolution images are still weeks away and will not be available until late August on the inbound leg when the spacecraft returns and swoops barely above the clouds.
“JunoCam will continue to take images as we go around in this first orbit,” said Candy Hansen, Juno co-investigator from the Planetary Science Institute, Tucson, Arizona, in a statement.
“The first high-resolution images of the planet will be taken on August 27 when Juno makes its next close pass to Jupiter.”
All of JunoCams images will be released to the public.
During a 20 month long science mission – entailing 37 orbits lasting 14 days each – the probe will plunge to within about 2,600 miles (4,100 kilometers) of the turbulent cloud tops.
It will collect unparalleled new data that will unveil the hidden inner secrets of Jupiter’s origin and evolution as it peers “beneath the obscuring cloud cover of Jupiter and study its auroras to learn more about the planet’s origins, structure, atmosphere and magnetosphere.”
The solar powered Juno spacecraft approached Jupiter over its north pole, affording an unprecedented perspective on the Jovian system – “which looks like a mini solar system” – as it flew through the giant planets intense radiation belts in ‘autopilot’ mode.
Juno is the first solar powered probe to explore Jupiter or any outer planet.
In the final weeks of the approach JunoCam captured dramatic views of Jupiter and all four of the Galilean Moons moons — Io, Europa, Ganymede and Callisto.
At the post JOI briefing on July 5, these were combined into a spectacular JunoCam time-lapse movie released by Bolton and NASA.
Watch and be mesmerized -“for humanity, our first real glimpse of celestial harmonic motion” says Bolton.
Video caption: NASA’s Juno spacecraft captured a unique time-lapse movie of the Galilean satellites in motion about Jupiter. The movie begins on June 12th with Juno 10 million miles from Jupiter, and ends on June 29th, 3 million miles distant. The innermost moon is volcanic Io; next in line is the ice-crusted ocean world Europa, followed by massive Ganymede, and finally, heavily cratered Callisto. Galileo observed these moons to change position with respect to Jupiter over the course of a few nights. From this observation he realized that the moons were orbiting mighty Jupiter, a truth that forever changed humanity’s understanding of our place in the cosmos. Earth was not the center of the Universe. For the first time in history, we look upon these moons as they orbit Jupiter and share in Galileo’s revelation. This is the motion of nature’s harmony. Credits: NASA/JPL-Caltech/MSSS
The $1.1 Billion Juno was launched on Aug. 5, 2011 from Cape Canaveral, Florida atop the most powerful version of the Atlas V rocket augmented by 5 solid rocket boosters and built by United Launch Alliance (ULA). That same Atlas V 551 version just launched MUOS-5 for the US Navy on June 24.
The Juno spacecraft was built by prime contractor Lockheed Martin in Denver.
The mission will end in February 2018 with an intentional death dive into the atmosphere to prevent any possibility of a collision with Europa, one of Jupiter’s moons that is a potential abode for life.
The last NASA spacecraft to orbit Jupiter was Galileo in 1995. It explored the Jovian system until 2003.
From Earth’s perspective, Jupiter was in conjunction with Earth’s Moon shortly after JOI during the first week in July.
Personally its thrilling to realize that an emissary from Earth is once again orbiting Jupiter after a 13 year long hiatus as seen in the authors image below – coincidentally taken the same day as JunoCam’s first image from orbit.
Juno, Jupiter and the Moon as seen from I-95 over Dunn, NC on July 10, 2016. Credit: Ken Kremer/kenkremer.com
Stay tuned here for Ken’s continuing Earth and Planetary science and human spaceflight news.
Learn more about Juno at Jupiter, SpaceX CRS-9 rocket launch, ISS, ULA Atlas and Delta rockets, Orbital ATK Cygnus, Boeing, Space Taxis, Mars rovers, Orion, SLS, Antares, NASA missions and more at Ken’s upcoming outreach events:
July 15-18: “SpaceX launches to ISS on CRS-9, Juno at Jupiter, ULA Delta 4 Heavy spy satellite, SLS, Orion, Commercial crew, Curiosity explores Mars, Pluto and more,” Kennedy Space Center Quality Inn, Titusville, FL, evenings
NASA’s Juno probe captured the image data for this composite picture during its Earth flyby on Oct. 9 over Argentina, South America and the southern Atlantic Ocean. Raw imagery was reconstructed and aligned by Ken Kremer and Marco Di Lorenzo, and false-color blue has been added to the view taken by a near-infrared filter that is typically used to detect methane. Credit: NASA/JPL/SwRI/MSSS/Ken Kremer/Marco Di Lorenzo
The three Lego figures inside: Galileo, Juno and Jupiter. Source: NASA
Given its historic importance – being just the second spacecraft to conduct a long-term mission to Jupiter – NASA was sure to outfit the Juno probe with some high-end memorabilia. These include the Galileo commemorative plaque*, which shows Galileo’s face and the words he wrote when he first observed Jupiter’s four largest moons in 1610 (known today as the Galilean Moons).
In addition, three commemorative figures (each measuring 4 cm high) were created especially for the mission. Created by Lego, these figurines depict the Roman god Jupiter, his wife Juno, and the astronomer Galileo Galilei – each holding an identifying object. Constructed from aluminum so they could withstand the trip and the radiation of the gas giant, these figures arrived with the probe around Jupiter on Monday, July 4th.
Much like the Juno spacecraft that is ferrying them, these figurines have spent the past 5 years in space and traversing the 869 million kilometers that lie between Earth from Jupiter. As part of Lego’s “Build Your Future” campaign, the trio are part of an educational outreach program to inspire kids around the world to learn about science and technology.
A key part of this effort is the Building Challenge launched by Lego to raise awareness about space exploration. For this challenge, participants are asked to build their vision of the future of space exploration using Lego bricks, take pictures of their creation, and then upload them to the Lego website’s “Mission to Space” gallery. The winning creations will be featured on LEGO.com and the Gallery homepage.
NASA’s Juno spacecraft launched on August 6, 2011 and should arrive at Jupiter on July 4, 2016. Credit: NASA / JPL
In addition, Lego’s website has new content that encourages children to learn more about the Solar System. As they state on the webpage:
“Have you ever wondered what it would be like if you could visit other planets and travel through space? Well, here’s your chance to go on a mission to Space through a partnership between NASA and LEGO Group! Pack your space lunch, and get ready to fly the International Space Station, pass the Moon, to Mars and Jupiter! Learn fun facts about our solar system, play quizzes, and get a taste of life as an astronaut and space pioneer! Round off the trip by entering an out-of-this-world building challenge.”
True to their mythological roots, the figurine of Jupiter (the Roman equivalent of Zeus) is holding a lightning bolt. Juno, his wife, is holding a magnifying glass, which represents her ability to see through the clouds that Jupiter surrounded himself with. And Galileo, the famed astronomer who was the first to view Jupiter’s moons, holds his famed telescope and an orb representing Jupiter.
These three figurines are the closest thing the Juno spacecraft has to a crew. During the next two years, they will be with the probe as it orbits Jupiter a total of 37 times, conducting surveys of Jupiter’s atmosphere, interior, magnetosphere, and gravitational field. When the mission is over, they will deorbit with the probe, crashing into Jupiter’s atmosphere to prevent any contamination of Jupiter’s moons.
Three LEGO figurines representing the Roman god Jupiter, his wife Juno and Galileo Galilei are shown here aboard the Juno spacecraft. Credits: NASA/JPL-Caltech/KSC
Over the course of the past three days, numerous memes have popped up across the internet, claiming that: “When Galileo first spotted Jupiter’s largest moons, he named them after Jove’s (Zeus’) mistresses. Now, a probe named after his wife will arrive in the system, thus fulfilling a joke astronomers have been setting up for the past 400 years!” – I’m paraphrasing, of course!
Nevertheless, the observation is an apt one. And to make this witty statement complete, all those figures who had a hand in lending Jupiter the cultural significant it has (be they historical or mythological) will be represented as Juno tries to unveil Jupiter’s mysteries. Sure, those likenesses are just 4 cm in height, and they are built out of aluminum instead of marble, but it’s the thought that counts!
*The Galileo commemorative plague contains script written in Italian by Galileo’s own hand. It reads:
“On the 11th it was in this formation, and the star closest to Jupiter was half the size than the other and very close to the other so that during the previous nights all of the three observed stars looked of the same dimension and among them equally afar; so that it is evident that around Jupiter there are three moving stars invisible till this time to everyone.”
And be sure to enjoy this video of NASA’s Juno team celebrating the probe’s arrival at Jupiter:
The Jovian planets of the Solar System. Credit: bork.hampshire.edu
Beyond our Solar System’s “Frost Line” – the region where volatiles like water, ammonia and methane begin to freeze – four massive planets reside. Though these planets – Jupiter, Saturn, Uranus and Neptune – vary in terms of size, mass, and composition, they all share certain characteristics that cause them to differ greatly from the terrestrial planets located in the inner Solar System.
Officially designated as gas (and/or ice) giants, these worlds also go by the name of “Jovian planets”. Used interchangeably with terms like gas giant and giant planet, the name describes worlds that are essentially “Jupiter-like”. And while the Solar System contains four such planets, extra-solar surveys have discovered hundreds of Jovian planets, and that’s just so far…
Definition:
The term Jovian is derived from Jupiter, the largest of the Outer Planets and the first to be observed using a telescope – by Galileo Galilei in 1610. Taking its name from the Roman king of the gods – Jupiter, or Jove – the adjective Jovian has come to mean anything associated with Jupiter; and by extension, a Jupiter-like planet.
The giant planets of the Solar System (aka. the Jovians). Credit: spiff.rit.edu
Within the Solar System, four Jovian planets exist – Jupiter, Saturn, Uranus and Neptune. A planet designated as Jovian is hence a gas giant, composed primarily of hydrogen and helium gas with varying degrees of heavier elements. In addition to having large systems of moons, these planets each have their own ring systems as well.
Another common feature of gas giants is their lack of a surface, at least when compared to terrestrial planets. In all cases, scientists define the “surface” of a gas giant (for the sake of defining temperatures and air pressure) as being the region where the atmospheric pressure exceeds one bar (the pressure found on Earth at sea level).
Structure and Composition:
In all cases, the gas giants of our Solar System are composed primarily of hydrogen and helium with the remainder being taken up by heavier elements. These elements correspond to a structure that is differentiated between an outer layer of molecular hydrogen and helium that surrounds a layer of liquid (or metallic) hydrogen or volatile elements, and a probable molten core with a rocky composition.
Due to difference in their structure and composition, the four gas giants are often differentiated, with Jupiter and Saturn being classified as “gas giants” while Uranus and Neptune are “ice giants”. This is due to the fact that Neptune and Uranus have higher concentrations of methane and heavier elements – like oxygen, carbon, nitrogen, and sulfur – in their interior.
Interior models of the giant planets, showing rocky cores overlaid by solid and gaseous envelopes. Credit: NASA/JPL
In stark contrast to the terrestrial planets, the density of the gas giants is slightly greater than that of water (1 g/cm³). The one exception to this is Saturn, where the mean density is actually lower than water (0.687 g/cm3). In all cases, temperature and pressure increase dramatically the closer one ventures into the core.
Atmospheric Conditions:
Much like their structures and compositions, the atmospheres and weather patterns of the four gas/ice giants are quite similar. The primary difference is that the atmospheres get progressively cooler the farther away they are from Sun. As a result, each Jovian planet has distinct cloud layers who’s altitudes are determined by their temperatures, such that the gases can condense into liquid and solid states.
In short, since Saturn is colder than Jupiter at any particular altitude, its cloud layers occur deeper within it’s atmosphere. Uranus and Neptune, due to their even lower temperatures, are able to hold condensed methane in their very cold tropospheres, whereas Jupiter and Saturn cannot.
The presence of this methane is what gives Uranus and Neptune their hazy blue color, where Jupiter is orange-white in appearance due to the intermingling of hydrogen (which gives off a red appearance), while the upwelling of phosphorus, sulfur, and hydrocarbons yield spotted patches areas and ammonia crystals create white bands.
Jupiter and Saturn have similar appearances, owing to their similar compositions and atmospheres. Credit: NASA/GSFC
The atmosphere of Jupiter is classified into four layers based on increasing altitude: the troposphere, stratosphere, thermosphere and exosphere. Temperature and pressure increase with depth, which leads to rising convection cells emerging that carry with them the phosphorus, sulfur, and hydrocarbons that interact with UV radiation to give the upper atmosphere its spotted appearance.
Saturn’s atmosphere is similar in composition to Jupiter’s. Hence why it is similarly colored, though its bands are much fainter and are much wider near the equator (resulting in a pale gold color). As with Jupiter’s cloud layers, they are divided into the upper and lower layers, which vary in composition based on depth and pressure. Both planets also have clouds composed of ammonia crystals in their upper atmospheres, with a possible thin layer of water clouds underlying them.
Uranus’ atmosphere can be divided into three sections – the innermost stratosphere, the troposphere, and the outer thermosphere. The troposphere is the densest layer, and also happens to be the coldest in the solar system. Within the troposphere are layers of clouds, with methane clouds on top, ammonium hydrosulfide clouds, ammonia and hydrogen sulfide clouds, and water clouds at the lowest pressures.
Next is the stratosphere, which contains ethane smog, acetylene and methane, and these hazes help warm this layer of the atmosphere. Here, temperatures increase considerably, largely due to solar radiation. The outermost layer (the thermosphere and corona) has a uniform temperature of 800-850 (577 °C/1,070 °F), though scientists are unsure as to the reason.
Uranus and Neptune, the Solar System’s ice giant planets. Credit: Wikipedia Commons
This is something that Uranus shares with Neptune, which also experiences unusually high temperatures in its thermosphere (about 750 K (476.85 °C/890 °F). Like Uranus, Neptune is too far from the Sun for this heat to be generated through the absorption of ultraviolet radiation, which means another heating mechanism is involved.
Neptune’s atmosphere is also predominantly hydrogen and helium, with a small amount of methane. The presence of methane is part of what gives Neptune its blue hue, although Neptune’s is darker and more vivid. Its atmosphere can be subdivided into two main regions: the lower troposphere (where temperatures decrease with altitude), and the stratosphere (where temperatures increase with altitude).
The lower stratosphere is believed to contain hydrocarbons like ethane and ethyne, which are the result of methane interacting with UV radiation, thus producing Neptune’s atmospheric haze. The stratosphere is also home to trace amounts of carbon monoxide and hydrogen cyanide, which are responsible for Neptune’s stratosphere being warmer than that of Uranus.
Weather Patterns:
Like Earth, Jupiter experiences auroras near its northern and southern poles. But on Jupiter, the auroral activity is much more intense and rarely ever stops. These are the result of Jupiter’s intense radiation, it’s magnetic field, and the abundance of material from Io’s volcanoes that react with Jupiter’s ionosphere.
Reprocessed view by Bjorn Jonsson of the Great Red Spot taken by Voyager 1 in 1979 reveals an incredible wealth of detail. Credit: NASA/JPL
Jupiter also experiences violent weather patterns. Wind speeds of 100 m/s (360 km/h) are common in zonal jets, and can reach as high as 620 kph (385 mph). Storms form within hours and can become thousands of km in diameter overnight. One storm, the Great Red Spot, has been raging since at least the late 1600s.
The storm has been shrinking and expanding throughout its history; but in 2012, it was suggested that the Giant Red Spot might eventually disappear. Jupiter also periodically experiences flashes of lightning in its atmosphere, which can be up to a thousand times as powerful as those observed here on the Earth.
Saturn’s atmosphere is similar, exhibiting long-lived ovals now and then that can be several thousands of kilometers wide. A good example is the Great White Spot (aka. Great White Oval), a unique but short-lived phenomenon that occurs once every 30 Earth years. Since 2010, a large band of white clouds called the Northern Electrostatic Disturbance have been observed enveloping Saturn, and is believed to be followed by another in 2020.
The winds on Saturn are the second fastest among the Solar System’s planets, which have reached a measured high of 500 m/s (1800 km/h). Saturn’s northern and southern poles have also shown evidence of stormy weather. At the north pole, this takes the form of a persisting hexagonal wave pattern measuring about 13,800 km (8,600 mi) and rotating with a period of 10h 39m 24s.
Saturn makes a beautifully striped ornament in this natural-color image, showing its north polar hexagon and central vortex. Credit: NASA/JPL-Caltech/Space Science Institute
The south pole vortex apparently takes the form of a jet stream, but not a hexagonal standing wave. These storms are estimated to be generating winds of 550 km/h, are comparable in size to Earth, and believed to have been going on for billions of years. In 2006, the Cassini space probe observed a hurricane-like storm that had a clearly defined eye. Such storms had not been observed on any planet other than Earth – even on Jupiter.
Uranus’s weather follows a similar pattern where systems are broken up into bands that rotate around the planet, which are driven by internal heat rising to the upper atmosphere. Winds on Uranus can reach up to 900 km/h (560 mph), creating massive storms like the one spotted by the Hubble Space Telescope in 2012. Similar to Jupiter’s Great Red Spot, this “Dark Spot” was a giant cloud vortex that measured 1,700 kilometers by 3,000 kilometers (1,100 miles by 1,900 miles).
Because Neptune is not a solid body, its atmosphere undergoes differential rotation, with its wide equatorial zone rotating slower than the planet’s magnetic field (18 hours vs. 16.1 hours). By contrast, the reverse is true for the polar regions where the rotation period is 12 hours. This differential rotation is the most pronounced of any planet in the Solar System, and results in strong latitudinal wind shear and violent storms.
Reconstruction of Voyager 2 images showing the Great Dar Spot (top left), Scooter (middle), and the Small Dark Spot (lower right). Credit: NASA/JPL
The first to be spotted was a massive anticyclonic storm measuring 13,000 x 6,600 km and resembling the Great Red Spot of Jupiter. Known as the Great Dark Spot, this storm was not spotted five later (Nov. 2nd, 1994) when the Hubble Space Telescope looked for it. Instead, a new storm that was very similar in appearance was found in the planet’s northern hemisphere, suggesting that these storms have a shorter life span than Jupiter’s.
Exoplanets:
Due to the limitations imposed by our current methods, most of the exoplanets discovered so far by surveys like the Kepler space observatory have been comparable in size to the giant planets of the Solar System. Because these large planets are inferred to share more in common with Jupiter than with the other giant planets, the term “Jovian Planet” has been used by many to describe them.
Many of these planets, being greater in mass than Jupiter, have also been dubbed as “Super-Jupiters” by astronomers. Such planets exist at the borderline between planets and brown dwarf stars, the smallest stars known to exist in our Universe. They can be up to 80 times more massive than Jupiter but are still comparable in size, since their stronger gravity compresses the material into an ever denser, more compact sphere.
Artist’s concept of the “Hot Jupiter” exoplanet HD 149026b. Credit: NASA/JPL-Caltech
Those Super-Jupiters that have distant orbits from their parent stars are known as “Cold Jupiters”, whereas those that have close orbits are called “Hot Jupiters”. A surprising number of Hot Jupiters have been observed by exoplanet surveys, due to the fact that they are particularly easy to spot using the Radial Velocity method – which measures the oscillation of parent stars due to the influence of their planets.
In the past, astronomers believed that Jupiter-like planets could only form in the outer reaches of a star system. However, the recent discovery of many Jupiter-sized planets orbiting close to their stars has cast doubt on this. Thanks to the discovery of Jovians beyond our Solar System, astronomers may be forced to rethink our models of planetary formation.
Since Galileo first observed Jupiter through his telescope, Jovian planets have been an endless source of fascination for us. And despite many centuries of research and progress, there are still many things we don’t know about them. Our latest effort to explore Jupiter, the Juno Mission, is expected to produce some rather interesting finds. Here’s hoping they bring us one step closer to understanding those darn Jovians!
Illustration of NASA's Juno spacecraft firing its main engine to slow down and go into orbit around Jupiter. Lockheed Martin built the Juno spacecraft for NASA's Jet Propulsion Laboratory. Credit: NASA/Lockheed Martin
Illustration of NASA’s Juno spacecraft firing its main engine to slow down and go into orbit around Jupiter. Lockheed Martin built the Juno spacecraft for NASA’s Jet Propulsion Laboratory. Credit: NASA/Lockheed Martin
“NASA did it again!” pronounced an elated Scott Bolton, investigator of Juno from Southwest Research Institute in San Antonio, to loud cheers and applause from the overflow crowd of mission scientists and media gathered at the post orbit media briefing at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, Calif.
After a nearly five year journey covering 1.7-billion-miles (2.8-billion-kilometers) across our solar system, NASA’s basketball court-sized Juno orbiter achieved orbit around Jupiter, the ‘King of the Planets’ late Monday night, July 4, in a gift to all Americans on our 240th Independence Day and a gift to science to elucidate our origins.
“We are in orbit and now the fun begins, the science,” said Bolton at the briefing. “We just did the hardest thing NASA’s ever done! That’s my claim. I am so happy … and proud of this team.”
And the science is all about peering far beneath the well known banded cloud tops for the first time to investigate Jupiter’s deep interior with a suite of nine instruments, and discover the mysteries of its genesis and evolution and the implications for how we came to be.
“The deep interior of Jupiter is nearly unknown. That’s what we are trying to learn about. The origin of us.”
Solar powered Juno successfully entered a polar elliptical orbit around Jupiter after completing a must-do 35-minute-long firing of the main engine known as Jupiter Orbital Insertion or JOI.
The spacecraft approached Jupiter over its north pole, affording an unprecedented perspective on the Jovian system – “which looks like a mini solar system” – as it flew through the giant planets intense radiation belts in ‘autopilot’ mode.
“The mission team did great. The spacecraft did great. We are looking great. It’s a great day,” Bolton gushes.
Engineers tracking the telemetry received confirmation that the JOI burn was completed as planned at 8:53 p.m. PDT (11:53 p.m. EDT) Monday, July 4.
Juno is only the second probe from Earth to orbit Jupiter and the first solar powered probe to the outer planets. The gas giant is two and a half times more massive than all of the other planets combined.
“Independence Day always is something to celebrate, but today we can add to America’s birthday another reason to cheer — Juno is at Jupiter,” said NASA administrator Charlie Bolden in a statement.
“And what is more American than a NASA mission going boldly where no spacecraft has gone before? With Juno, we will investigate the unknowns of Jupiter’s massive radiation belts to delve deep into not only the planet’s interior, but into how Jupiter was born and how our entire solar system evolved.”
Artists concept NASA’s Juno spacecraft firing its main engine to slow down and go into orbit around Jupiter on July 4, 2016 nearly five years after launch. Credit: NASA
The do-or-die burn of Juno’s 645-Newton Leros-1b main engine started at 8:18 p.m. PDT (11:18 p.m. EDT), which had the effect of decreasing the spacecraft’s velocity by 1,212 miles per hour (542 meters per second) and allowing Juno to be captured in orbit around Jupiter. There were no second chances.
All of the science instruments were turned off on June 30 to keep the focus on the nail-biting insertion maneuver and preserve battery power, said Bolton.
“So tonight through tones Juno sang to us. And it was a song of perfection. After a 1.7 billion mile journey we hit tour burn targets within one second,” Rick Nybakken, Juno project manager from JPL, gleefully reported at the briefing.
“That’s how good our team is! And that’s how well our Juno spacecraft performed tonight.”
To accomplish the burn, the spacecraft first had to adjust it’s attitude to point the engine in the required direction to slow the spacecraft and then simultaneously also had the effect that the life giving solar panels were pointing away from the sun. It the only time during the entire mission at Jupiter that the solar panels were in darkness and not producing energy.
The spacecraft’s rotation rate was also spun up from 2 to 5 revolutions per minute (RPM) to help stabilize it during JOI. Juno is spin stabilized to maintain pointing.
After the burn was complete, Juno was spun down and adjusted to point to the sun before it ran out of battery power.
We have to get the blood flowing through Juno’s veins, Bolton emphasized.
It is equipped with 18,698 individual solar cells over 60 square meters of surface on the solar arrays to provide energy. Juno is spinning like a windmill through space with its 3 giant solar arrays. It is about 540 million miles (869 million kilometers) from Earth.
Juno mission briefing on July 5, 2016 at JPL after the successful JOI orbit insertion on July 4. Credit: Roland Keller/rkeusa.blogspot.com
Signals traveling at the speed of light take 48 minutes to reach Earth, said Nybakken.
So the main engine burn, which was fully automated, was already over for some 13 minutes before the first indications of the outcome reach Earth via a series of Doppler signals and tones.
“Tonight, 540 million miles away, Juno performed a precisely choreographed dance at blazing speeds with the largest, most intense planet in our solar system,” said Guy Beutelschies, director of Interplanetary Missions at Lockheed Martin Space Systems.
“Since launch, Juno has operated exceptionally well, and the flawless orbit insertion is a testament to everyone working on Juno and their focus on getting this amazing spacecraft to its destination. NASA now has a science laboratory orbiting Jupiter.”
“The spacecraft is now pointed back at the sun and the antenna back at Earth. The spacecraft performed well and did everything it needed to do,” he reported at the briefing.
“We are looking forward to getting all that science data to Scott and the team.”
“Juno is also the farthest mission to rely on solar power. And although they provide only 1/25th the power at Earth, they still provide over 500 watts of power at Jupiter,” said Nybakken.
Initially the spacecraft enters a long, looping polar orbit lasting about 53 days. That highly elliptical orbit will be trimmed to 14 days for the regular science orbits.
The orbits are designed to minimize contact with Jupiter’s extremely intense radiation belts. The nine science instruments are shielded inside a ½ thick vault built of Titanium to protect them from the utterly deadly radiation of some 20,000,000 rads.
During a 20 month long science mission – entailing 37 orbits lasting 14 days each – the probe will plunge to within about 3000 miles of the turbulent cloud tops and collect unprecedented new data that will unveil the hidden inner secrets of Jupiter’s origin and evolution.
But the length and number of the science orbits has changed since the mission was launched almost 5 years ago in 2011.
Originally Juno was planned to last about one year with an orbital profile involving 33 orbits of 11 days each.
I asked the team to explain the details of how and why the change from 11 to 14 days orbits and increasing the total number of orbits to 37 from 33, especially in light of the extremely harsh radiation hazards?
“The original plan of 33 orbits of 11 days was an example but there were other periods that would work,” Bolton told Universe Today.
“What we really cared about was dropping down over the poles and capturing each longitude, and laying a map or net around Jupiter.”
“Also, during the Earth flyby we went into safe mode. And as we looked at that it was a hiccup by the spacecraft but it actually behaved as it should have.”
“So we said well if that happened at Jupiter we would like to be able to recover and not lose an orbit. So we started to look at the timeline of how long it took to recover, and did we want to add a couple of days to the orbit for conservatism – to ensure the science mission.”
“So it made sense to add 3 days. It didn’t change the science and it made the probability of success even greater. So that was the basis of the change.”
“We also evaluated the radiation. And it wasn’t much different. Juno is designed to take data at a very low risk. The radiation slowly accumulates at the start. As you get to the later part of the mission, it gets a faster and faster accumulation.”
“So we still retained that conservatism as well and the overall radiation dose was pretty much the same,” Bolton explained.
“The radiation we accumulate is not just the more time you spend the more radiation,” Steve Levin, Juno Project Scientist at JPL, told Universe Today.
“Each time we come in close to the planet we get a dose of radiation. Then the spacecraft is out far from Jupiter and is relatively free from that radiation until we come in close again.”
“So just changing from 11 to 14 day orbits does not mean we get more radiation because you are there longer.”
“It’s really the number of times we come in close to Jupiter that determines how much radiation we are getting.”
Juno is the fastest spacecraft ever to arrive at Jupiter and was moving at over 165,000 mph relative to Earth and 130,000 mph relative to Jupiter at the moment of JOI.
Juno’s principal goal is to understand the origin and evolution of Jupiter.
“With its suite of nine science instruments, Juno will investigate the existence of a solid planetary core, map Jupiter’s intense magnetic field, measure the amount of water and ammonia in the deep atmosphere, and observe the planet’s auroras. The mission also will let us take a giant step forward in our understanding of how giant planets form and the role these titans played in putting together the rest of the solar system. As our primary example of a giant planet, Jupiter also can provide critical knowledge for understanding the planetary systems being discovered around other stars,” according to a NASA description.
The $1.1 Billion Juno was launched on Aug. 5, 2011 from Cape Canaveral, Florida atop the most powerful version of the Atlas V rocket augmented by 5 solid rocket boosters and built by United Launch Alliance (ULA). That same Atlas V 551 version just launched MUOS-5 for the US Navy on June 24.
The Juno spacecraft was built by prime contractor Lockheed Martin in Denver.
United Launch Alliance Atlas V liftoff with NASA’s Juno to Jupiter orbiter on Aug. 5, 2011 from Cape Canaveral Air Force Station, Florida. Credit: Ken Kremer/kenkremer.com
The last NASA spacecraft to orbit Jupiter was Galileo in 1995. It explored the Jovian system until 2003.
Bolton also released new views of Jupiter taken by JunoCam – the on board public outreach camera that snapped a final gorgeous view of the Jovian system showing Jupiter and its four largest moons, dancing around the largest planet in our solar system.
The newly released color image was taken on June 29, 2016, at a distance of 3.3 million miles (5.3 million kilometers) from Jupiter – just before the probe went into autopilot mode.
This is the final view taken by the JunoCam instrument on NASA’s Juno spacecraft before Juno’s instruments were powered down in preparation for orbit insertion. Juno obtained this color view on June 29, 2016, at a distance of 3.3 million miles (5.3 million kilometers) from Jupiter. See timelapse movie below. Credits: NASA/JPL-Caltech/MSSS
It shows a dramatic view of the clouds bands of Jupiter, dominating a spectacular scene that includes the giant planet’s four largest moons — Io, Europa, Ganymede and Callisto.
Scott Bolton and NASA also released this spectacular new time-lapse JunoCam movie at today’s briefing showing Juno’s approach to Jupiter and the Galilean Moons.
Watch and be mesmerized -“for humanity, our first real glimpse of celestial harmonic motion” says Bolton.
Video caption: NASA’s Juno spacecraft captured a unique time-lapse movie of the Galilean satellites in motion about Jupiter. The movie begins on June 12th with Juno 10 million miles from Jupiter, and ends on June 29th, 3 million miles distant. The innermost moon is volcanic Io; next in line is the ice-crusted ocean world Europa, followed by massive Ganymede, and finally, heavily cratered Callisto. Galileo observed these moons change position with respect to Jupiter over the course of a few nights. From this observation he realized that the moons were orbiting mighty Jupiter, a truth that forever changed humanity’s understanding of our place in the cosmos. Earth was not the center of the Universe. For the first time in history, we look upon these moons as they orbit Jupiter and share in Galileo’s revelation. This is the motion of nature’s harmony. Credits: NASA/JPL-Caltech/MSSS
Along the 5 year journey to Jupiter, Juno made a return trip to Earth on Oct. 9, 2013 for a flyby gravity assist speed boost that enabled the trek to the Jovian system.
During the Earth flyby (EFB), the science team observed Earth using most of Juno’s nine science instruments including, JunoCam, since the slingshot also served as an important dress rehearsal and key test of the spacecraft’s instruments, systems and flight operations teams.
The JunoCam images will be made publicly available to see and process.
During the Earth flyby, Junocam snapped some striking images of Earth as it sped over Argentina, South America and the South Atlantic Ocean and came within 347 miles (560 kilometers) of the surface.
For example a dazzling portrait of our Home Planet high over the South American coastline and the Atlantic Ocean gives a hint of what’s to come from Jupiter’s cloud tops. See our colorized Junocam mosaic of land, sea and swirling clouds, created by Ken Kremer and Marco Di Lorenzo
This colorized composite shows more than half of Earth’s disk over the coast of Argentina and the South Atlantic Ocean as the Juno probe slingshotted by on Oct. 9, 2013 for a gravity assisted acceleration to Jupiter. The mosaic was assembled from raw images taken by the Junocam imager. Credit: NASA/JPL/SwRI/MSSS/Ken Kremer/Marco Di Lorenzo
Stay tuned here for Ken’s continuing Earth and Planetary science and human spaceflight news.
Rick Nybakken, Juno project manager at JPL illustrates how Juno will enter orbit around Jupiter during Juno mission briefing on July 4, 2016 at JPL. Credit: Roland Keller/rkeusa.blogspot.com
