The Moon, just a couple days before new phase and the upcoming partial solar eclipse, joins Venus and Mars in the dawn sky on Thursday Sept. 10. Well below the triplet, look for returning Jupiter. Source: Stellarium
The dawn sky’s where it’s happening. With Saturn swiftly sinking westward at dusk, bright planets have become scarce in the evening hours. But if you get up early and look east, you’ll discover where the party is. Venus, Mars and now Jupiter have the dance floor.
Tale of two crescents. A montage of the thick crescent Moon and crescent Venus photographed earlier this month. Credit: Tom Ruen
What’s more, the sky gods have seen fit to roll a thin crescent Moon alongside Venus Thursday morning (Sept. 10). This lovely twinning of crescents is best seen about 75 minutes to an hour before sunrise. All you need is a pair of 10x binoculars to see the peewee Venusian version. Its waning crescent phase closely mimics the Moon’s.
From the U.S., the separation between the two will vary from 3° for the East Coast to 4.5° for the West. European and African skywatchers will witness the actual conjunction with the Moon gliding 2.5° north of the planet.
Venus is very bright, making it easy to see in the daytime if you know where to look. Try using the thin Moon soon after sunrise (7:30 a.m. local time shown here) to spot Venus. Aim and focus your binoculars on the Moon, then glide up and to the right to find Venus. If you succeed, lower the binoculars and see if you can spot it without optical aid. Source: Stellarium
Much fainter Mars, checking in at magnitude +1.8, lies 6° to the left or east of the Moon. It thrills me to see Mars begin a new apparition with its return to the morning sky. Next year, the Red Planet reaches opposition on May 22 in the constellation Scorpius, when it will be brighter than Sirius and more than 18 arc seconds across, its biggest and closest since 2005.
Remember Jupiter? We lost it in the solar glare more than a month ago, but if you can find a location with a nice, open eastern horizon, you can welcome the ever-jovial planet back Thursday. Bring binoculars just in case! Jove’s only a few degrees high in moderately-bright twilight.
The bright sunlit crescent contrasts with the darker lighting of twice-reflected light contributed by own planet. Credit: Bob King
When you look at the Moon Thursday, most of it will be illuminated not by sunlight but by Earth-light called earthshine. This smoky, dark glow results from sunlight bouncing off the globe into space to softly light the otherwise shadowed portion of the Moon. The effect is most pleasing to the eye and remarkable in binoculars, which reveal lunar seas and even larger craters shrouded in blue-dark. Don’t miss it!
The Universe is a very big place, and we occupy a very small corner of it. Known as the Solar System, our stomping grounds are not only a tiny fraction of the Universe as we know it, but is also a very small part of our galactic neighborhood (aka. the Milky Way Galaxy). When it comes right down to it, our world is just a drop of water in an endless cosmic sea.
Nevertheless, the Solar System is still a very big place, and one which is filled with its fair share of mysteries. And in truth, it was only within the relatively recent past that we began to understand its true extent. And when it comes to exploring it, we’ve really only begun to scratch the surface.
Discovery:
With very few exceptions, few people or civilizations before the era of modern astronomy recognized the Solar System for what it was. In fact, the vast majority of astronomical systems posited that the Earth was a stationary object and that all known celestial objects revolved around it. In addition, they viewed it as being fundamentally different from other stellar objects, which they held to be ethereal or divine in nature.
Although there were some Greek, Arab and Asian astronomers during Antiquity and the Medieval period who believed that the universe was heliocentric in nature (i.e. that the Earth and other bodies revolved around the Sun) it was not until Nicolaus Copernicus developed his mathematically predictive model of a heliocentric system in the 16th century that it began to become widespread.
Galileo (1564 – 1642) would often show people how to use his telescope to view the sky in Saint Mark’s square in Venice. Note the lack of adaptive optics. Credit: Public Domain
During the 17th-century, scientists like Galileo Galilei, Johannes Kepler, and Isaac Newton developed an understanding of physics which led to the gradual acceptance that the Earth revolves round the Sun. The development of theories like gravity also led to the realization that the other planets are governed by the same physical laws as Earth.
The widespread use of the telescope also led to a revolution in astronomy. After Galileo discovered the moons of Jupiter in 1610, Christian Huygens would go on to discover that Saturn also had moons in 1655. In time, new planets would also be discovered (such as Uranus and Neptune), as well as comets (such as Halley’s Comet) and the Asteroids Belt.
By the 19th century, three observations made by three separate astronomers determined the true nature of the Solar System and its place the universe. The first was made in 1839 by German astronomer Friedrich Bessel, who successfully measured an apparent shift in the position of a star created by the Earth’s motion around the Sun (aka. stellar parallax). This not only confirmed the heliocentric model beyond a doubt, but revealed the vast distance between the Sun and the stars.
In 1859, Robert Bunsen and Gustav Kirchhoff (a German chemist and physicist) used the newly invented spectroscope to examined the spectral signature of the Sun. They discovered that it was composed of the same elements as existed on Earth, thus proving that Earth and the heavens were composed of the same elements.
With parallax technique, astronomers observe object at opposite ends of Earth’s orbit around the Sun to precisely measure its distance. Credit: Alexandra Angelich, NRAO/AUI/NSF.
Then, Father Angelo Secchi – an Italian astronomer and director at the Pontifical Gregorian University – compared the spectral signature of the Sun with those of other stars, and found them to be virtually identical. This demonstrated conclusively that our Sun was composed of the same materials as every other star in the universe.
Further apparent discrepancies in the orbits of the outer planets led American astronomer Percival Lowell to conclude that yet another planet, which he referred to as “Planet X“, must lie beyond Neptune. After his death, his Lowell Observatory conducted a search that ultimately led to Clyde Tombaugh’s discovery of Pluto in 1930.
Also in 1992, astronomers David C. Jewitt of the University of Hawaii and Jane Luu of the MIT discovered the Trans-Neptunian Object (TNO) known as (15760) 1992 QB1. This would prove to be the first of a new population, known as the Kuiper Belt, which had already been predicted by astronomers to exist at the edge of the Solar System.
Further investigation of the Kuiper Belt by the turn of the century would lead to additional discoveries. The discovery of Eris and other “plutoids” by Mike Brown, Chad Trujillo, David Rabinowitz and other astronomers would lead to the Great Planet Debate – where IAU policy and the convention for designating planets would be contested.
The Sun contains 99.86% of the system’s known mass, and its gravity dominates the entire system. Most large objects in orbit around the Sun lie near the plane of Earth’s orbit (the ecliptic) and most planets and bodies rotate around it in the same direction (counter-clockwise when viewed from above Earth’s north pole). The planets are very close to the ecliptic, whereas comets and Kuiper belt objects are frequently at greater angles to it.
It’s four largest orbiting bodies (the gas giants) account for 99% of the remaining mass, with Jupiter and Saturn together comprising more than 90%. The remaining objects of the Solar System (including the four terrestrial planets, the dwarf planets, moons, asteroids, and comets) together comprise less than 0.002% of the Solar System’s total mass.
The Sun and planets to scale. Credit: Illustration by Judy Schmidt, texture maps by Björn Jónsson
Astronomers sometimes informally divide this structure into separate regions. First, there is the Inner Solar System, which includes the four terrestrial planets and the Asteroid Belt. Beyond this, there’s the outer Solar System that includes the four gas giant planets. Meanwhile, there’s the outermost parts of the Solar System are considered a distinct region consisting of the objects beyond Neptune (i.e. Trans-Neptunian Objects).
Most of the planets in the Solar System possess secondary systems of their own, being orbited by planetary objects called natural satellites (or moons). In the case of the four giant planets, there are also planetary rings – thin bands of tiny particles that orbit them in unison. Most of the largest natural satellites are in synchronous rotation, with one face permanently turned toward their parent.
The Sun, which comprises nearly all the matter in the Solar System, is composed of roughly 98% hydrogen and helium. The terrestrial planets of the Inner Solar System are composed primarily of silicate rock, iron and nickel. Beyond the Asteroid Belt, planets are composed mainly of gases (such as hydrogen, helium) and ices – like water, methane, ammonia, hydrogen sulfide and carbon dioxide.
Objects farther from the Sun are composed largely of materials with lower melting points. Icy substances comprise the majority of the satellites of the giant planets, as well as most of Uranus and Neptune (hence why they are sometimes referred to as “ice giants”) and the numerous small objects that lie beyond Neptune’s orbit.
Together, gases and ices are referred to as volatiles. The boundary in the Solar System beyond which those volatile substances could condense is known as the frost line, which lies roughly 5 AU from the Sun. Within the Kuiper Belt, objects and planetesimals are composed mainly of these materials and rock.
Formation and Evolution:
The Solar System formed 4.568 billion years ago from the gravitational collapse of a region within a large molecular cloud composed of hydrogen, helium, and small amounts of heavier elements fused by previous generations of stars. As the region that would become the Solar System (known as the pre-solar nebula) collapsed, conservation of angular momentum caused it to rotate faster.
The center, where most of the mass collected, became increasingly hotter than the surrounding disc. As the contracting nebula rotated faster, it began to flatten into a protoplanetary disc with a hot, dense protostar at the center. The planets formed by accretion from this disc, in which dust and gas gravitated together and coalesced to form ever larger bodies.
Due to their higher boiling points, only metals and silicates could exist in solid form closer to the Sun, and these would eventually form the terrestrial planets of Mercury, Venus, Earth, and Mars. Because metallic elements only comprised a very small fraction of the solar nebula, the terrestrial planets could not grow very large.
In contrast, the giant planets (Jupiter, Saturn, Uranus, and Neptune) formed beyond the point between the orbits of Mars and Jupiter where material is cool enough for volatile icy compounds to remain solid (i.e. the frost line).
The ices that formed these planets were more plentiful than the metals and silicates that formed the terrestrial inner planets, allowing them to grow massive enough to capture large atmospheres of hydrogen and helium. Leftover debris that never became planets congregated in regions such as the asteroid belt, Kuiper belt, and Oort cloud.
Within 50 million years, the pressure and density of hydrogen in the center of the protostar became great enough for it to begin thermonuclear fusion. The temperature, reaction rate, pressure, and density increased until hydrostatic equilibrium was achieved.
At this point, the Sun became a main-sequence star. Solar wind from the Sun created the heliosphere and swept away the remaining gas and dust from the protoplanetary disc into interstellar space, ending the planetary formation process.
The terrestrial planets of our Solar System at approximately relative sizes. From left, Mercury, Venus, Earth and Mars. Credit: Lunar and Planetary Institute
The Solar System will remain roughly as we know it today until the hydrogen in the core of the Sun has been entirely converted to helium. This will occur roughly 5 billion years from now and mark the end of the Sun’s main-sequence life. At this time, the core of the Sun will collapse, and the energy output will be much greater than at present.
The outer layers of the Sun will expand to roughly 260 times its current diameter, and the Sun will become a red giant. The expanding Sun is expected to vaporize Mercury and Venus and render Earth uninhabitable as the habitable zone moves out to the orbit of Mars. Eventually, the core will be hot enough for helium fusion and the Sun will burn helium for a time, after which nuclear reactions in the core will start to dwindle.
At this point, the Sun’s outer layers will move away into space, leaving a white dwarf – an extraordinarily dense object that will have half the original mass of the Sun, but will be the size of Earth. The ejected outer layers will form what is known as a planetary nebula, returning some of the material that formed the Sun to the interstellar medium.
Inner Solar System:
In the inner Solar System, we find the “Inner Planets” – Mercury, Venus, Earth, and Mars – which are so named because they orbit closest to the Sun. In addition to their proximity, these planets have a number of key differences that set them apart from planets elsewhere in the Solar System.
For starters, the inner planets are rocky and terrestrial, composed mostly of silicates and metals, whereas the outer planets are gas giants. The inner planets are also much more closely spaced than their outer Solar System counterparts. In fact, the radius of the entire region is less than the distance between the orbits of Jupiter and Saturn.
Generally, inner planets are smaller and denser than their counterparts, and have few to no moons or rings circling them. The outer planets, meanwhile, often have dozens of satellites and rings composed of particles of ice and rock.
The terrestrial inner planets are composed largely of refractory minerals such as the silicates, which form their crusts and mantles, and metals such as iron and nickel which form their cores. Three of the four inner planets (Venus, Earth and Mars) have atmospheres substantial enough to generate weather. All of them have impact craters and tectonic surface features as well, such as rift valleys and volcanoes.
Of the inner planets, Mercury is the closest to our Sun and the smallest of the terrestrial planets. Its magnetic field is only about 1% that of Earth’s, and it’s very thin atmosphere means that it is hot during the day (up to 430°C) and freezing at night (as low as -187 °C) because the atmosphere can neither keep heat in or out. It has no moons of its own and is comprised mostly of iron and nickel. Mercury is one of the densest planets in the Solar System.
Venus, which is about the same size as Earth, has a thick toxic atmosphere that traps heat, making it the hottest planet in the Solar System. This atmosphere is composed of 96% carbon dioxide, along with nitrogen and a few other gases. Dense clouds within Venus’ atmosphere are composed of sulphuric acid and other corrosive compounds, with very little water. Much of Venus’ surface is marked with volcanoes and deep canyons – the biggest of which is over 6400 km (4,000 mi) long.
Earth is the third inner planet and the one we know best. Of the four terrestrial planets, Earth is the largest, and the only one that currently has liquid water, which is necessary for life as we know it. Earth’s atmosphere protects the planet from dangerous radiation and helps keep valuable sunlight and warmth in, which is also essential for life to survive.
Like the other terrestrial planets, Earth has a rocky surface with mountains and canyons, and a heavy metal core. Earth’s atmosphere contains water vapor, which helps to moderate daily temperatures. Like Mercury, the Earth has an internal magnetic field. And our Moon, the only one we have, is comprised of a mixture of various rocks and minerals.
Mars, as it appears today, Credit: NASA
Mars is the fourth and final inner planet, and is also known as the “Red Planet” due to the oxidization of iron-rich materials that form the planet’s surface. Mars also has some of the most interesting terrain features of any of the terrestrial planets. These include the largest mountain in the Solar System (Olympus Mons) which rises some 21,229 m (69,649 ft) above the surface, and a giant canyon called Valles Marineris – which is 4000 km (2500 mi) long and reaches depths of up to 7 km (4 mi).
Much of Mars’ surface is very old and filled with craters, but there are geologically newer areas of the planet as well. At the Martian poles are polar ice caps that shrink in size during the Martian spring and summer. Mars is less dense than Earth and has a smaller magnetic field, which is indicative of a solid core, rather than a liquid one.
Mars’ thin atmosphere has led some astronomers to believe that the surface water that once existed there might have actually taken liquid form, but has since evaporated into space. The planet has two small moons called Phobos and Deimos.
Outer Solar System:
The outer planets (sometimes called Jovian planets or gas giants) are huge planets swaddled in gas that have rings and plenty of moons. Despite their size, only two of them are visible without telescopes: Jupiter and Saturn. Uranus and Neptune were the first planets discovered since antiquity, and showed astronomers that the solar system was bigger than previously thought.
The outer planets of our Solar System at approximately relative sizes. From left, Jupiter, Saturn, Uranus and Neptune. Credit: Lunar and Planetary Institute
Jupiter is the largest planet in our Solar System and spins very rapidly (10 Earth hours) relative to its orbit of the sun (12 Earth years). Its thick atmosphere is mostly made up of hydrogen and helium, perhaps surrounding a terrestrial core that is about Earth’s size. The planet has dozens of moons, some faint rings and a Great Red Spot – a raging storm that has happening for the past 400 years at least.
Saturn is best known for its prominent ring system – seven known rings with well-defined divisions and gaps between them. How the rings got there is one subject under investigation. It also has dozens of moons. Its atmosphere is mostly hydrogen and helium, and it also rotates quickly (10.7 Earth hours) relative to its time to circle the Sun (29 Earth years).
Uranus was first discovered by William Herschel in 1781. The planet’s day takes about 17 Earth hours and one orbit around the Sun takes 84 Earth years. Its mass contains water, methane, ammonia, hydrogen and helium surrounding a rocky core. It has dozens of moons and a faint ring system. The only spacecraft to visit this planet was the Voyager 2 spacecraft in 1986.
Neptune is a distant planet that contains water, ammmonia, methane, hydrogen and helium and a possible Earth-sized core. It has more than a dozen moons and six rings. NASA’s Voyager 2 spacecraft also visited this planet and its system by 1989 during its transit of the outer Solar System.
How many moons are there in the Solar System? Image credit: NASA
Trans-Neptunian Region:
There have been more than a thousand objects discovered in the Kuiper Belt, and it’s theorized that there are as many as 100,000 objects larger than 100 km in diameter. Given to their small size and extreme distance from Earth, the chemical makeup of KBOs is very difficult to determine.
However, spectrographic studies conducted of the region since its discovery have generally indicated that its members are primarily composed of ices: a mixture of light hydrocarbons (such as methane), ammonia, and water ice – a composition they share with comets. Initial studies also confirmed a broad range of colors among KBOs, ranging from neutral grey to deep red.
This suggests that their surfaces are composed of a wide range of compounds, from dirty ices to hydrocarbons. In 1996, Robert H. Brown et al. obtained spectroscopic data on the KBO 1993 SC, revealing its surface composition to be markedly similar to that of Pluto (as well as Neptune’s moon Triton) in that it possessed large amounts of methane ice.
Water ice has been detected in several KBOs, including 1996 TO66, 38628 Huya and 20000 Varuna. In 2004, Mike Brown et al. determined the existence of crystalline water ice and ammonia hydrate on one of the largest known KBOs, 50000 Quaoar. Both of these substances would have been destroyed over the age of the Solar System, suggesting that Quaoar had been recently resurfaced, either by internal tectonic activity or by meteorite impacts.
Keeping Pluto company out in the Kuiper belt are many other objects worthy of mention. Quaoar, Makemake, Haumea, Orcus and Eris are all large icy bodies in the Belt and several of them even have moons of their own. These are all tremendously far away, and yet, very much within reach.
Oort Cloud and Farthest Regions:
The Oort Cloud is thought to extend from between 2,000 and 5,000 AU (0.03 and 0.08 ly) to as far as 50,000 AU (0.79 ly) from the Sun, though some estimates place the outer edge as far as 100,000 and 200,000 AU (1.58 and 3.16 ly). The Cloud is thought to be comprised of two regions – a spherical outer Oort Cloud of 20,000 – 50,000 AU (0.32 – 0.79 ly), and disc-shaped inner Oort (or Hills) Cloud of 2,000 – 20,000 AU (0.03 – 0.32 ly).
The outer Oort cloud may have trillions of objects larger than 1 km (0.62 mi), and billions that measure 20 kilometers (12 mi) in diameter. Its total mass is not known, but – assuming that Halley’s Comet is a typical representation of outer Oort Cloud objects – it has the combined mass of roughly 3×1025 kilograms (6.6×1025 pounds), or five Earths.
The layout of the solar system, including the Oort Cloud, on a logarithmic scale. Credit: NASA
Based on the analyses of past comets, the vast majority of Oort Cloud objects are composed of icy volatiles – such as water, methane, ethane, carbon monoxide, hydrogen cyanide, and ammonia. The appearance of asteroids thought to be originating from the Oort Cloud has also prompted theoretical research that suggests that the population consists of 1-2% asteroids.
Earlier estimates placed its mass up to 380 Earth masses, but improved knowledge of the size distribution of long-period comets has led to lower estimates. The mass of the inner Oort Cloud, meanwhile, has yet to be characterized. The contents of both Kuiper Belt and the Oort Cloud are known as Trans-Neptunian Objects (TNOs), because the objects of both regions have orbits that that are further from the Sun than Neptune’s orbit.
Exploration:
Our knowledge of the Solar System also benefited immensely from the advent of robotic spacecraft, satellites, and robotic landers. Beginning in the mid-20th century, in what was known as “The Space Age“, manned and robotic spacecraft began exploring planets, asteroids and comets in the Inner and Outer Solar System.
All planets in the Solar System have now been visited to varying degrees by spacecraft launched from Earth. Through these unmanned missions, humans have been able to get close-up photographs of all the planets. In the case of landers and rovers, tests have been performed on the soils and atmospheres of some.
Photograph of a Russian technician putting the finishing touches on Sputnik 1, humanity’s first artificial satellite. Credit: NASA/Asif A. Siddiqi
The first artificial object sent into space was the Soviet satellite Sputnik 1, which was launched in space in 1957, successfully orbited the Earth for months, and collected information on the density of the upper atmosphere and the ionosphere. The American probe Explorer 6, launched in 1959, was the first satellite to capture images of the Earth from space.
Robotic spacecraft conducting flybys also revealed considerable information about the planet’s atmospheres, geological and surface features. The first successful probe to fly by another planet was the Soviet Luna 1 probe, which sped past the Moon in 1959. The Mariner program resulted in multiple successful planetary flybys, consisting of the Mariner 2 mission past Venus in 1962, the Mariner 4 mission past Mars in 1965, and the Mariner 10 mission past Mercury in 1974.
By the 1970’s, probes were being dispatched to the outer planets as well, beginning with the Pioneer 10 mission which flew past Jupiter in 1973 and the Pioneer 11 visit to Saturn in 1979.The Voyager probes performed a grand tour of the outer planets following their launch in 1977, with both probes passing Jupiter in 1979 and Saturn in 1980-1981. Voyager 2 then went on to make close approaches to Uranus in 1986 and Neptune in 1989.
Launched on January 19th, 2006, the New Horizons probe is the first man-made spacecraft to explore the Kuiper Belt. This unmanned mission flew by Pluto in July 2015. Should it prove feasible, the mission will also be extended to observe a number of other Kuiper Belt Objects (KBOs) in the coming years.
Orbiters, rovers, and landers began being deployed to other planets in the Solar System by the 1960’s. The first was the Soviet Luna 10 satellite, which was sent into lunar orbit in 1966. This was followed in 1971 with the deployment of the Mariner 9 space probe, which orbited Mars, and the Soviet Venera 9 which orbited Venus in 1975.
The Galileo probe became the first artificial satellite to orbit an outer planet when it reached Jupiter in 1995, followed by the Cassini–Huygens probe orbiting Saturn in 2004. Mercury and Vesta were explored by 2011 by the MESSENGER and Dawn probes, respectively, with Dawn establishing orbit around the asteroid/dwarf planet Ceres in 2015.
The first probe to land on another Solar System body was the Soviet Luna 2 probe, which impacted the Moon in 1959. Since then, probes have landed on or impacted on the surfaces of Venus in 1966 (Venera 3), Mars in 1971 (Mars 3 and Viking 1 in 1976), the asteroid 433 Eros in 2001 (NEAR Shoemaker), and Saturn’s moon Titan (Huygens) and the comet Tempel 1 (Deep Impact) in 2005.
Curiosity Rover self portrait mosaic, taken with the MAHLI camera while sitting on flat sedimentary rocks at the “John Klein” outcrop in Feb. 2013. Credit: NASA/JPL-Caltech/MSSS/Marco Di Lorenzo/KenKremer
To date, only two worlds in the Solar System, the Moon and Mars, have been visited by mobile rovers. The first robotic rover to land on another planet was the Soviet Lunokhod 1, which landed on the Moon in 1970. The first to visit another planet was Sojourner, which traveled 500 meters across the surface of Mars in 1997, followed by Spirit(2004), Opportunity (2004), and Curiosity (2012).
Manned missions into space began in earnest in the 1950’s, and was a major focal point for both the United States and Soviet Union during the “Space Race“. For the Soviets, this took the form of the Vostok program, which involved sending manned space capsules into orbit.
The first mission – Vostok 1 – took place on April 12th, 1961, and was piloted by Soviet cosmonaut Yuri Gagarin (the first human being to go into space). On June 6th, 1963, the Soviets also sent the first woman – Valentina Tereshvoka – into space as part of the Vostok 6 mission.
In the US, Project Mercury was initiated with the same goal of placing a crewed capsule into orbit. On May 5th, 1961, astronaut Alan Shepard went into space aboard the Freedom 7mission and became the first American (and second human) to go into space.
After the Vostok and Mercury programs were completed, the focus of both nations and space programs shifted towards the development of two and three-person spacecraft, as well as the development of long-duration spaceflights and extra-vehicular activity (EVA).
Bootprint in the moon dust from Apollo 11. Credit: NASA
This took the form of the Voshkod and Gemini programs in the Soviet Union and US, respectively. For the Soviets, this involved developing a two to three-person capsule, whereas the Gemini program focused on developing the support and expertise needed for an eventual manned mission to the Moon.
These latter efforts culminated on July 21st, 1969 with the Apollo 11 mission, when astronauts Neil Armstrong and Buzz Aldrin became the first men to walk on the Moon. As part of the Apollo program, five more Moon landings would take place through 1972, and the program itself resulted in many scientific packages being deployed on the Lunar surface, and samples of moon rocks being returned to Earth.
After the Moon Landing took place, the focus of the US and Soviet space programs then began to shift to the development of space stations and reusable spacecraft. For the Soviets, this resulted in the first crewed orbital space stations dedicated to scientific research and military reconnaissance – known as the Salyut and Almaz space stations.
The first orbital space station to host more than one crew was NASA’s Skylab, which successfully held three crews from 1973 to 1974. The first true human settlement in space was the Soviet space station Mir, which was continuously occupied for close to ten years, from 1989 to 1999. It was decommissioned in 2001, and its successor, the International Space Station, has maintained a continuous human presence in space since then.
Space Shuttle Columbia launching on its maiden voyage on April 12th, 1981. Credit: NASA
The United States’ Space Shuttle, which debuted in 1981, became the only reusable spacecraft to successfully make multiple orbital flights. The five shuttles that were built (Atlantis, Endeavour, Discovery, Challenger, Columbiaand Enterprise) flew a total of 121 missions before being decommissioned in 2011.
During their history of service, two of the craft were destroyed in accidents. These included the Space Shuttle Challenger – which exploded upon take-off on Jan. 28th, 1986 – and the Space Shuttle Columbia which disintegrated during re-entry on Feb. 1st, 2003.
In 2004, then-U.S. President George W. Bush announced the Vision for Space Exploration, which called for a replacement for the aging Shuttle, a return to the Moon and, ultimately, a manned mission to Mars. These goals have since been maintained by the Obama administration, and now include plans for an Asteroid Redirect mission, where a robotic craft will tow an asteroid closer to Earth so a manned mission can be mounted to it.
All the information gained from manned and robotic missions about the geological phenomena of other planets – such as mountains and craters – as well as their seasonal, meteorological phenomena (i.e. clouds, dust storms and ice caps) have led to the realization that other planets experience much the same phenomena as Earth. In addition, it has also helped scientists to learn much about the history of the Solar System and its formation.
As our exploration of the Inner and Outer Solar System has improved and expanded, our conventions for categorizing planets has also changed. Our current model of the Solar System includes eight planets (four terrestrial, four gas giants), four dwarf planets, and a growing number of Trans-Neptunian Objects that have yet to be designated. It also contains and is surrounded by countless asteroids and planetesimals.
Given its sheer size, composition and complexity, researching our Solar System in full detail would take an entire lifetime. Obviously, no one has that kind of time to dedicate to the topic, so we have decided to compile the many articles we have about it here on Universe Today in one simple page of links for your convenience.
There are thousands of facts about the solar system in the links below. Enjoy your research.
We know that in space, no one can hear you scream. But what would things sound like on another planet?
When humans finally set foot on Mars, they’re going to be curious about everything around them.
What’s under that rock? What does it feel like to jump in the lower Martian gravity. What does Martian regolith taste like? What’s the bitcoin to red rock exchange rate?
As long as they perform their activities in the safety of a pressurized habitation module or exosuit, everything should be fine. But what does Mars sound like?
I urge all future Martian travelers, no matter how badly you want to know the answer to this question: don’t take your helmet off. With only 1% the atmospheric pressure of Earth, you’d empty your lungs with a final scream in a brief and foolish moment, then suffocate horribly with a mouthful of dust on the surface of the Red Planet.
But… actually, even the screaming would sound a little different. How different? Let me show you. First you just need to take your helmet off for a just a little sec, just an itsy bitsy second. Here, I’ll hold it for you. Oh, come on, just take your helmet off. All the cool kids are doing it.
What about Venus? Or Titan? What would everything sound like on an alien world?
We evolved to exist on Earth, and so it’s perfectly safe for us to listen to sounds in the air. No space suit needed. Unless you didn’t evolve on Earth, in which case I offer to serve as emissary to our all new alien overlords.
You know sounds travel when waves of energy propagate through a medium, like air or water. The molecules bump into each other and pass along the energy until they strike something that won’t move, like your ear drum. Then your brain turns bouncing into sounds.
The speed of the waves depends on what the medium is made of and how dense it is. For example, sound travels at about 340 meters/second in dry air, at sea level at room temperature. Sound moves much more quickly through liquid. In water it’s nearly 1,500 m/s. It’s even faster through a solid – iron is up past 5,100 m/s. Our brain perceives a different sound depending on the intensity of the waves and how quickly they bounce off our ears.
Artist’s impression of the surface of Venus. Credit: ESA/AOES
Other worlds have media that sound waves can travel through, and with your eardrum exposed to the atmosphere you should theoretically hear sounds on other worlds. Catastrophic biological failures from using your eardrums outside of documented pressure tolerances notwithstanding.
Professor Tim Leighton and a team of researchers from the University of Southampton have simulated what we would hear standing on the surface of other worlds, like Mars, Venus or even Saturn’s Moon Titan.
On Venus, the pitch of your voice would become deeper, because vocal cords would vibrate much more slowly in the thicker Venusian atmosphere. But sounds would travel more quickly through the soupy atmosphere. According to Dr. Leighton, humans would sound like bass Smurfs. Mars would sound a little bit higher, and Titan would sound totally alien.
Dr. Leighton actually simulated the same sound on different worlds. Here’s the sound of thunder on Earth.
Here’s what it would sound like on Venus.
And here’s what it would sound like on Mars.
Here’s what a probe splashing into water on Earth would sound like.
And here’s what it would sound like splashing into a hydrocarbon lake on Titan.
You might be amazed to learn that we still haven’t actually recorded sounds on another world, right up until someone points out that putting a microphone on another planet hasn’t been that big a priority for any space mission.
A fish-eye view of Titan’s surface from the European Space Agency’s Huygens lander in January 2005. Credit: ESA/NASA/JPL/University of Arizona
Especially when we could analyze soil samples, but hey fart sounds played and then recorded in the Venusian atmosphere could prove incredibly valuable to the future of internet soundboards.
The Planetary Society has been working to get a microphone included on a mission. They actually included a microphone on the Mars Polar Lander mission that failed in 1999. Another French mission was going to have a microphone, but it was cancelled. There are no microphones on either Spirit or Opportunity, and the Curiosity Rover doesn’t have one either despite its totally bumping stereo.
Here’s is the only thing we’ve got. When NASA’s Phoenix Lander reached the Red Planet in 2008, it had a microphone on board to capture sounds. It recorded audio as it entered the atmosphere, but operators turned the instrument off before it reached the surface because they were worried it would interfere with the landing.
Meh. I’m going to need you to do better NASA. I want an actual microphone recording winds on the surface of Mars. I hope it’s something Dethklok puts on their next album, they could afford that kind of expense.
It turns out, that if you travel to an alien world, not only would the sights be different, but the sounds would be alien too. Of course, you’d never know because you’re be too chicken to take your helmet off and take in the sounds through the superheated carbon dioxide or methane atmosphere.
What sounds would you like to hear on an alien world? Tell us in the comments below.
Venus dwindles to a captivating crescent nearly 1 arc minute across as seen on August 8, 2015. An infrared filter was used to increase contrast between the planet and otherwise bright sky. Credit: SEN / Damian Peach
Venus is HUGE right now but oh-so-skinny as it approaches inferior conjunction on August 15. Like crescents? You’ll never see a thinner and more elegant one, but first you’ll have to find it. Here’s how.
On August 9th, Venus is only 6 days before inferior conjunction when it passes between the Earth and Sun. Shortly before, during and after conjunction, Venus will appear as a wire-thin crescent. The planet will continue moving west of the Sun and rise higher in the morning sky after mid-August with greatest elongation west occurring on October 26, when its phase will fatten to half. Wikipedia with additions by the author
There’s only one drawback to enjoying Venus at its radically thinnest — it’s very close to the Sun and visible only during the daytime. A look at the diagram above reveals that as Venus and Earth draw closer, the planet also aligns with the Sun. At conjunction on August 15, it will pass 7.9° south of our star, appearing as an impossibly thin crescent in the solar glare. The sight is unique, a curved strand of incandescent wire burning in the blue.
Venus at inferior conjunction on January 10, 2014 shows both the sunlit crescent and cusp extensions caused by sunlight penetrating the atmosphere from behind. During this previous inferior conjunction, Venus passed north of the Sun, so we see the bottom of the crescent illuminated. Credit: Tudorica Alexandru
If you’re patient and the air is steady, you might even glimpse the cusps of the illuminated crescent extending beyond their normal length to partially or even completely encircle Venus’s disk. These thread-like extensions become visible when the planet lies almost directly between us and the Sun. Sunlight scatters off the Venus’s dense atmosphere, causing it to glow faintly along the limb. One of the most remarkable sights in the sky, the sight is testament to the thickness of the planet’s airy envelope.
Going, going, gone! Venus photographed in its beautiful crescent phase on two occasions last week. When the planet reaches inferior conjunction this Saturday (August 15), the crescent will expand to nearly 1 arc minute across. No planet comes closer to Earth than Venus — just 27 million miles this week. Credit: Giorgio Rizzarelli
Today, only 1.7% of the planet is illuminated by the Sun, which shines some 11° to the northwest. The Venusian crescent spans 57 arc seconds from tip to tip, very close to 1 arc minute or 1/30 the width of the Full Moon. Come conjunction day August 15, those numbers will be 0.9% and 58 arc seconds. The angular resolution of the human eye is 1 minute, implying that the planet’s shape might be within grasp of someone with excellent eyesight under a clear, clean, cloudless sky. However — and this is a big however — a bright sky and nearby Sun make this practically impossible.
No worries though. Even 7x binoculars will nail it; the trick is finding Venus in the first place. For binocular users, hiding the Sun COMPLETELY behind a building, chimney, power pole or tree is essential. The goddess lurks dangerously close to our blindingly-bright star, so you must take every precaution to protect your eyes. Never allow direct sunlight into your glass. Never look directly at the Sun – even for a second – with your eyes or UV and infrared light will sear your retinas. You can use the map provided, which shows several locations of the planet at 1 p.m. CDT when it’s highest in the sky, to help you spot it.
The Sun’s position is shown for 1 p.m. local daylight time facing due south, while Venus and its corresponding phase is depicted before, at and after conjunction. As Venus moves from left to right south of the Sun, its phase changes from evening crescent (left) to morning crescent from our perspective on Earth. Source: Stellarium with additions by the author
If you’d like to see Venus on a different day or time, download a free sky-charting program like Stellarium or Cartes du Ciel. With Stellarium, open the Sky and Viewing Options menu (F4) and click the Light Pollution Level option down to “1” to show Venus in a daytime sky. Pick a viewing time, note Venus’s orientation with respect to the Sun (which you’ve hidden of course!) and look at that spot in the sky with binoculars. I’ll admit, it’s a challenging observation requiring haze-free skies, but be persistent.
By coincidence, the Moon and Venus will be about the same distance from the Sun and appear as very similar thin crescents around 1 p.m. CDT on August 13. Venus should still be visible using the methods described below, but the Moon will be impossible to see. Source: Stellarium
A safer and more sure-fire way to track the planet down involves using those setting circles on your telescope mount most of us never bother with. First, find the celestial coordinates (right ascension and declination) of the Sun and Venus for the time you’d like to view. For example, let’s say we want to find Venus on August 10 at 2 p.m. Using your free software, you click on the Sun and Venus’s positions for that time of day to get their coordinates, in this case:
Venus – Right ascension 9h 42 minutes, declination +6°.
Sun – RA 9h 22 minutes, dec. +15° 30 minutes
Now subtract the two to get Venus’ offset from the Sun = 20 minutes east, 9.5° south.
Dust off those setting circles (declination shown here, marked off in degrees) and use them to point you to Venus this week. Credit: Bob King
Next, polar align your telescope using a compass and then cover the objective end with a safe mylar or glass solar filter. Center and sharply focus the Sun in the telescope. Now, loosen the RA lock and carefully offset the right ascension 20 minutes east using your setting circle, then re-lock. Do the same with declination, pointing the telescope 9.5° south of the Sun. If you’re polar alignment is reasonably good, when you remove the solar filter and look through the eyepiece, you should see Venus staring back at you from a blue sky. If you see nothing at first, nudge it a little this way and that to bring the planet into view.
Sometimes it takes me a couple tries, but I eventually stumble arrive on target. Obviously, you can also use this technique to spot Mercury and Jupiter in the daytime, too. By the way, don’t worry what the RA and Dec. read on your setting circles when you begin your hunt; only the offset’s important.
When inferior conjunction occurs at the same time Venus crosses the plane of Earth’s orbit, we see a rare transit (upper right) like this one on June 5, 2012. Credit: Bob King
This year’s conjunction is one of the best for finding Venus in daylight because it’s relatively far from the Sun. With an orbital inclination of 3.2°, Venus’s position can range up to 8° north and south of the Earth’s orbital plane or ecliptic. Rarely does the planet cross the ecliptic at the same time as inferior conjunction. When it does, we experience a transit of Venus. Transits always come in pairs; the last set occurred in 2004 and 2012; the next will happen over 100 years from now in 2117 and 2125.
I hope you’re able to make the most of this opportunity while still respecting your tender retinas. Good luck!
A radar view of Venus taken by the Magellan spacecraft, with some gaps filled in by the Pioneer Venus orbiter. Credit: NASA/JPL
As the morning star, the evening star, and the brightest natural object in the sky (after the Moon), human beings have been aware of Venus since time immemorial. Even though it would be many thousands of years before it was recognized as being a planet, its has been a part of human culture since the beginning of recorded history.
Because of this, the planet has played a vital role in the mythology and astrological systems of countless peoples. With the dawn of the modern age, interest in Venus has grown, and observations made about its position in the sky, changes in appearance, and similar characteristics to Earth have taught us much about our Solar System.
Size, Mass, and Orbit:
Because of its similar size, mass, proximity to the Sun, and composition, Venus is often referred to as Earth’s “sister planet”. With a mass of 4.8676×1024 kg, a surface area of 4.60 x 108 km², and a volume of 9.28×1011 km3, Venus is 81.5% as massive as Earth, and has 90% of its surface area and 86.6% of its volume.
Venus orbits the Sun at an average distance of about 0.72 AU (108,000,000 km/67,000,000 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.
Size comparison of Venus and Earth. Credit: NASA/JPL/Magellan
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 (making it the closest planet to Earth). This takes place, on average, once every 584 days. 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 sidereal day on Venus lasts longer than a Venusian year.
Composition and Surface Features:
Little direct information is available on the internal structure of Venus. However, based on its similarities in mass and density to Earth, scientists believe that they share a similar internal structure – a core, mantle, and crust. Like that of Earth, the Venusian core is believed to be at least be partially liquid because the two planets have been cooling at about the same rate.
One difference between the two planets is the lack of evidence for plate tectonics, which could be due to its crust being too strong to subduct without water to make it less viscous. This results in reduced heat loss from the planet, preventing it from cooling and the possibility that internal heat is lost in periodic major resurfacing events. This is also suggested as a possible reason for why Venus has no internally generated magnetic field.
The internal structure of Venus – the crust (outer layer), the mantle (middle layer) and the core (yellow inner layer). Credit: Wikipedia Commons
Venus’ surface appears to have been shaped by extensive volcanic activity. Venus also has several times as many volcanoes as Earth, and has 167 large volcanoes that are over 100 km across. The presence of these volcanoes is due to the lack of plate tectonics, which results in an older, more preserved crust. Whereas Earth’s oceanic crust is subject to subduction at its plate boundaries, and is on average ~100 million years old, the Venusian surface is estimated to be 300-600 million years of age.
There are indications that volcanic activity may be ongoing on Venus. Missions performed by the Soviet space program in 1970s and more recently by the European Space Agency have detected lightning storms in Venus’ atmosphere. Since Venus does not experience rainfall (except in the form of sulfuric acid), it has been theorized that the lightning is being caused by a volcanic eruption.
Other evidence is the periodic rise and fall of sulfur dioxide concentrations in the atmosphere, which could be the result of periodic, large volcanic eruptions. And finally, localized infrared hot spots (likely to be in the range of 800 – 1100 K) have appeared on the surface, which could represent lava freshly released by volcanic eruptions.
The preservation of Venus’ surface is also responsible for its impact craters, which are impeccably preserved. Almost a thousand craters exist, which are evenly distributed across the surface and range from 3 km to 280 km in diameter. No craters smaller than 3 km exist because of the effect the dense atmosphere has on incoming objects.
3-D perspective of the Venusian volcano, Maat Mons generated from radar data from NASA’s Magellan mission.
Essentially, objects with less than a certain amount of kinetic energy are slowed down so much by the atmosphere that they do not create an impact crater. And incoming projectiles less than 50 meters in diameter will fragment and burn up in the atmosphere before reaching the ground.
Atmosphere and Climate:
Surface observations of Venus have been difficult in the past, due to its extremely dense atmosphere, which is composed primarily of carbon dioxide with a small amount of nitrogen. At 92 bar (9.2 MPa), the atmospheric mass is 93 times that of Earth’s atmosphere and the pressure at the planet’s surface is about 92 times that at Earth’s surface.
Venus is also the hottest planet in our Solar System, with a mean surface temperature of 735 K (462 °C/863.6 °F). This is due to the CO²-rich atmosphere which, along with thick clouds of sulfur dioxide, generates the strongest greenhouse effect in the Solar System. Above the dense CO² layer, thick clouds consisting mainly of sulfur dioxide and sulfuric acid droplets scatter about 90% of the sunlight back into space.
The surface of Venus is effectively isothermal, which means that their is virtually no variation in Venus’ surface temperature between day and night, or the equator and the poles. The planet’s minute axial tilt – less than 3° compared to Earth’s 23° – also minimizes seasonal temperature variation. The only appreciable variation in temperature occurs with altitude.
The highest point on Venus, Maxwell Montes, is therefore the coolest point on the planet, with a temperature of about 655 K (380 °C) and an atmospheric pressure of about 4.5 MPa (45 bar).
Another common phenomena is Venus’ strong winds, which reach speeds of up to 85 m/s (300 km/h; 186.4 mph) at the cloud tops and circle the planet every four to five Earth days. At this speed, these winds move up to 60 times the speed of the planet’s rotation, whereas Earth’s fastest winds are only 10-20% of the planet’s rotational speed.
Venus flybys have also indicated that its dense clouds are capable of producing lightning, much like the clouds on Earth. Their intermittent appearance indicates a pattern associated with weather activity, and the lightning rate is at least half of that on Earth.
Historical Observations:
Although ancients peoples knew about Venus, some of the cultures thought it was two separate celestial objects – the evening star and the morning star. Although the Babylonians realized that these two “stars” were in fact the same object – as indicated in the Venus tablet of Ammisaduqa, dated 1581 BCE – it was not until the 6th century BCE that this became a common scientific understanding.
Many cultures have identified the planet with their respective goddess of love and beauty. Venus is the Roman name for the goddess of love, while the Babylonians named it Ishtar and the Greeks called it Aphrodite. The Romans also designated the morning aspect of Venus Lucifer (literally “Light-Bringer”) and the evening aspect as Vesper (“evening”, “supper”, “west”), both of which were literal translations of the respective Greek names (Phosphorus and Hesperus).
Venus approaches the Sun in a 2012 transit visible from Earth. Credit: NASA
The transit of Venus in front of the Sun was first observed in 1032 by the Persian astronomer Avicenna, who concluded that Venus is closer to Earth than the Sun. In the 12th century, the Andalusian astronomer Ibn Bajjah observed two black spots in front of the sun, which were later identified as the transits of Venus and Mercury by Iranian astronomer Qotb al-Din Shirazi in the 13th century.
Modern Observations:
By the early 17th century, the transit of Venus was observed by English astronomer Jeremiah Horrocks on December 4th, 1639, from his home. William Crabtree, a fellow English astronomer and friend of Horrocks’, observed the transit at the same time, also from his home.
When the Galileo Galilei first observed the planet in the early 17th century, he found it showed phases like the Moon, varying from crescent to gibbous to full, and vice versa. This behavior, which could only be possible if Venus’ orbited the Sun, became part of Galileo’s challenge to the Ptolemaic geocentric model and his advocacy of the Copernican heliocentric model.
The atmosphere of Venus was discovered in 1761 by Russian polymath Mikhail Lomonosov, and then observed in 1790 by German astronomer Johann Schröter. Schröter found when the planet was a thin crescent, the cusps extended through more than 180°. He correctly surmised this was due to the scattering of sunlight in a dense atmosphere.
Artist’s impression of the surface of Venus Credit: ESA/AOES
In December 1866, American astronomer Chester Smith Lyman made observations of Venus from the Yale Observatory, where he was on the board of managers. While observing the planet, he spotted a complete ring of light around the dark side of the planet when it was at inferior conjunction, providing further evidence for an atmosphere.
Little else was discovered about Venus until the 20th century, when the development of spectroscopic, radar, and ultraviolet observations made it possible to scan the surface. The first UV observations were carried out in the 1920s, when Frank E. Ross found that UV photographs revealed considerable detail, which appeared to be the result of a dense, yellow lower atmosphere with high cirrus clouds above it.
Spectroscopic observations in the early 20th century also gave the first clues about the Venusian rotation. Vesto Slipher tried to measure the Doppler shift of light from Venus. After finding that he could not detect any rotation, he surmised the planet must have a very long rotation period. Later work in the 1950s showed the rotation was retrograde.
Radar observations of Venus were first carried out in the 1960s, and provided the first measurements of the rotation period, which were close to the modern value. Radar observations in the 1970s, using the radio telescope at the Arecibo Observatory in Puerto Rico revealed details of the Venusian surface for the first time – such as the presence of the Maxwell Montes mountains.
Exploration of Venus:
The first attempts to explore Venus were mounted by the Soviets in the 1960s through the Venera Program. The first spacecraft, Venera-1 (also known in the west as Sputnik-8) was launched on February 12th, 1961. However, contact was lost seven days into the mission when the probe was about 2 million km from Earth. By mid-may, it was estimated that the probe had passed within 100,000 km (62,000 miles) of Venus.
The Mariner 1 and 2 spacecrafts made their way to Venus. Mariner 2 was the first successful Venus Flyby on . Credit: NASA/JPL
The United States launched the Mariner 1 probe on July 22nd, 1962, with the intent of conducting a Venus flyby; but here too, contact was lost during launch. The Mariner 2 mission, which launched on December 14th, 1962, became the first successful interplanetary mission and passed within 34,833 km (21,644 mi) of Venus’ surface.
Its observations confirmed earlier ground-based observations which indicated that though the cloud tops were cool, the surface was extremely hot – at least 425 °C (797 °F). This put an end all speculation that the planet might harbor life. Mariner 2 also obtained improved estimates of Venus’s mass, but was unable to detect either a magnetic field or radiation belts.
The Venera-3 spacecraft was the Soviets second attempt to reach Venus, and their first attempted to place a lander on the planet’s surface. The spacecraft cash-landed on Venus on March 1st, 1966, and was the first man-made object to enter the atmosphere and strike the surface of another planet. Unfortunately, its communication system failed before it was able to return any planetary data.
On October 18th, 1967, the Soviets tried again with the Venera-4 spacecraft. After reaching the planet, the probe successfully entered the atmosphere and began studying the atmosphere. In addition to noting the prevalence of carbon dioxide (90-95%), it measured temperatures in excess of what Mariner 2 observed, reaching almost 500 °C. Due to the thickness of Venus’ atmosphere, the probe descended slower than anticipated, and its batteries ran out after 93 minutes when the probe was still 24.96 km from the surface.
The Mariner 10 spacecraft. Credit: NASA/JPL
One day later, on October 19th, 1967, Mariner 5 conducted a fly-by at a distance of less than 4000 km above the cloud tops. Originally built as a backup for the Mars-bound Mariner 4, the probe was refitted for a Venus mission after Venera-4‘s success. The probe managed to collect information on the composition, pressure and density of the Venusian atmosphere, which was then analyzed alongside the Venera-4 data by a Soviet-American science team during a series of symposiums.
Venera-5 and Venera-6 were launched in January of 1969, and reached Venus on 16th and 17th of May. Taking into account the extreme density and pressure of Venus’ atmosphere, these probes were able to achieve a faster descent and reached an altitude of 20 km before being crushed – but not before returning over 50 minutes of atmospheric data.
The Venera-7 was built with the intent of returning data from the planet’s surface, and was construed with a reinforced descent module capable of withstanding intense pressure. While entering the atmosphere on December 15th, 1970, the probe crashed on the surface, apparently due to a ripped parachute. Luckily, it managed to return 23 minutes of temperature data and the first telemetry from the another planet’s surface before going offline.
The Soviets launched three more Venera probes between 1972 and 1975. The first landed on Venus on July 22nd, 1972, and managed to transmit data for 50 minutes. Venera-9 and 10 – which entered Venus’ atmosphere on October 22nd and October 25th, 1975, respectively – both managed to send back images of Venus’ surface, the first images ever taken of another planet’s landscape.
Images of Venusian surface taken by the Venera 10 lander on October 25th, 1977. Credit: Russian Space Web/Donald Mitchell
On November 3rd, 1973, the United States had sent the Mariner 10probe on a gravitational slingshot trajectory past Venus on its way to Mercury. By February 5th, 1974, the probe passed within 5790 km of Venus, returning over 4000 photographs. The images, which were the best to date, showed the planet to be almost featureless in visible light; but revealed never-before-seen details about the clouds in ultraviolet light.
By the late seventies, NASA commenced the Pioneer Venus Project, which consisted of two separate missions. The first was the Pioneer Venus Orbiter, which inserted into an elliptical orbit around Venus on December 4th, 1978, where it studied its atmosphere and mapped the surface for a period of 13 days. The second, the Pioneer Venus Multiprobe, released a total of four probes which entered the atmosphere on December 9th, 1978, returning data on its composition, winds and heat fluxes.
Four more Venera lander missions took place between the late 70s and early 80s. Venera 11 and Venera 12 detected Venusian electrical storms; and Venera 13 andVenera 14 landed on the planet on March 1st and 5th, 1982, returning the first color photographs of the surface. The Venera program came to a close in October 1983, when Venera 15 and Venera 16 were placed in orbit to conduct mapping of the Venusian terrain with synthetic aperture radar.
In 1985, the Soviets participated in a collaborative venture with several European states to launch the Vega Program. This two-spacecraft initiative was intended to take advantage of the appearance of Halley’s Comet in the inner Solar System, and combine a mission to it with a flyby of Venus. While en route to Halley on June 11th and 15th, the two Vega spacecraft dropped Venera-style probes supported by balloons into the upper atmosphere – which discovered that it was more turbulent than previously estimated, and subject to high winds and powerful convection cells.
The first color pictures taken of the surface of Venus by the Venera-13 space probe. Credit: NASA
NASA’s Magellan spacecraft was launched on May 4th, 1989, with a mission to map the surface of Venus with radar. In the course of its four and a half year mission, Magellan provided the most high-resolution images to date of the planet and was able to map 98% of the surface and 95% of its gravity field. In 1994, at the end of its mission, Magellan was sent to its destruction into the atmosphere of Venus to quantify its density.
Venus was observed by the Galileo and Cassini spacecraft during flybys on their respective missions to the outer planets, but Magellan was the last dedicated mission to Venus for over a decade. It was not until October of 2006 and June of 2007 that the MESSENGER probe would conduct a flyby of Venus (and collect data) in order to slow its trajectory for an eventual orbital insertion of Mercury.
The Venus Express, a probe designed and built by the European Space Agency, successfully assumed polar orbit around Venus on April 11th, 2006. This probe conducted a detailed study of the Venusian atmosphere and clouds, and discovered an ozone layer and a swirling double-vortex at the south pole before concluding its mission in December of 2014.
Future Missions:
The Japan Aerospace Exploration Agency (JAXA) devised a Venus orbiter – Akatsuki (formerly “Planet-C”) – to conduct surface imaging with an infrared camera, studies on Venus’ lightning, and to determine the existence of current volcanism. The craft was launched on May 20th, 2010, but the craft failed to enter orbit in December 2010. Its main engine is still offline, but its controllers will attempt to use its small attitude control thrusters to make another orbital insertion attempt on December 7th, 2015.
Artist’s concept of the Venus in Situ explorer mission, which could be deployed to Venus by 2022. Credit: NASA
In late 2013, NASA launched the Venus Spectral Rocket Experiment, a sub-orbital space telescope. This experimented is intended to conduct ultraviolet light studies of Venus’s atmosphere, for the purpose of learning more about the history of water on Venus.
The European Space Agency’s (ESA) BepiColombo mission, which will launch in January 2017, will perform two flybys of Venus before it reaches Mercury orbit in 2020. NASA will launch the Solar Probe Plusin 2018, which will perform seven Venus flybys during its six-year mission to study the Sun.
Under its New Frontiers Program, NASA has proposed mounting a lander mission to Venus called the Venus In-Situ Explorer by 2022. The purpose will be to study Venus’ surface conditions and investigate the elemental and mineralogical features of the regolith. The probe would be equipped with a core sampler to drill into the surface and study pristine rock samples not weathered by the harsh surface conditions.
The Venera-D spacecraft is a proposed Russian space probe to Venus, which is scheduled to be launched around 2024. This mission will conduct remote-sensing observations around the planet and deploy a lander, based on the Venera design, capable of surviving for a long duration on the surface.
Because of its proximity to Earth, and its similarity in size, mass and composition, Venus was once believed to hold life. In fact, the idea of Venus being a tropical world persisted well into the 20th century, until the Venera and Mariner programs demonstrated the absolute hellish conditions that actually exist on the planet.
Nevertheless, it is believed that Venus may once have been much like Earth, with a similar atmosphere and warm, flowing water on its surface. This notion is supported by the fact that Venus sits within the inner edge of the Sun’s habitable zone and has an ozone layer. However, owing to the runaway greenhouse effect and the lack of a magnetic field, this water disappeared many billions of years ago.
Still, there are those who believed that Venus could one day support human colonies. Currently, the atmospheric pressure near to the ground is far too extreme for settlements to be built on the surface. But 50 km above the surface, both the temperature and air pressure are similar to Earth’s, and both nitrogen and oxygen are believed to exist. This has led to proposals for “floating cities” to be built in the Venusian atmosphere and the exploration of the atmosphere using Airships.
In addition, proposals have been made suggesting the Venus should be terraformed. These have ranged from installing a huge space-shade to combat the greenhouse effect, to crashing comets into the surface to blow the atmosphere off. Other ideas involve converting the atmosphere using calcium and magnesium to sequester the carbon away.
Much like proposals to terraform Mars, these ideas are all in their infancy and are hard-pressed to address the long-term challenges associated with changing the planet’s climate. However, they do show that humanity’s fascination with Venus has not diminished over time. From being a central to our mythology and the first star we saw in the morning (and the last one we saw at night), Venus has since gone on to become a subject of fascination for astronomers and a possible prospect for off-world real estate.
But until such time as technology improves, Venus will remain Earth’s hostile and inhospitable “sister planet”, with intense pressure, sulfuric acid rains, and a toxic atmosphere.
The terrestrial planets of our Solar System at approximately relative sizes. From left, Mercury, Venus, Earth and Mars. Credit: Lunar and Planetary Institute
In studying our Solar System over the course of many centuries, astronomers learned a great deal about the types of planets that exist in our universe. This knowledge has since expanded thanks to the discovery of extrasolar planets, many of which are similar to what we have observed here at home.
For example, while hundreds of gas giants of varying size have been detected (which are easier to detect because of their size), numerous planets have also been spotted that are similar to Earth – aka. “Earth-like”. These are what is known as terrestrial planets, a designation which says a lot about a planet how it came to be.
Definition:
Also known as a telluric or rocky planet, a terrestrial planet is a celestial body that is composed primarily of silicate rocks or metals and has a solid surface. This distinguishes them from gas giants, which are primarily composed of gases like hydrogen and helium, water, and some heavier elements in various states.
The term terrestrial planet is derived from the Latin “Terra” (i.e. Earth). Terrestrial planets are therefore those that are “Earth-like”, meaning they are similar in structure and composition to planet Earth.
Artist’s concept for the range of Earth-like extrasolar planets that have been discovered in recent years. Credit: NASA/JPL
Composition and Characteristics:
All terrestrial planets have approximately the same type of structure: a central metallic core composed of mostly iron, with a surrounding silicate mantle. Such planets have common surface features, which include canyons, craters, mountains, volcanoes, and other similar structures, depending on the presence of water and tectonic activity.
Terrestrial planets also have secondary atmospheres, which are generated through volcanism or comet impacts. This also differentiates them from gas giants, where the planetary atmospheres are primary and were captured directly from the original solar nebula.
Terrestrial planets are also known for having few or no moons. Venus and Mercury have no moons, while Earth has only the one (the Moon). Mars has two satellites, Phobos and Deimos, but these are more akin to large asteroids than actual moons. Unlike the gas giants, terrestrial planets also have no planetary ring systems.
The Earth’s interior structure, shown here as consisting of multiple “layers”. Credit: discovermagazine.com
Solar Terrestrial Planets:
All those planets found within the Inner Solar System – Mercury, Venus, Earth and Mars – are examples of terrestrial planets. Each are composed primarily of silicate rock and metal, which is differentiated between a dense, metallic core and a silicate mantle. The Moon is similar, but has a much smaller iron core.
Io and Europa are also satellites that have internal structures similar to that of terrestrial planets. In the case of the former, models of the moon’s composition suggest that the mantle is composed primarily of silicate rock and iron, which surrounds a core of iron and iron sulphide. Europa, on the other hand, is believed to have an iron core that is surrounded by an outer layer of water.
Dwarf planets, like Ceres and Pluto, and other large asteroids are similar to terrestrial planets in the fact that they do have a solid surface. However, they differ in that they are, on average, composed of more icy materials than rock.
Extrasolar Terrestrial Planets:
Most of the planets detected outside of the Solar System have been gas giants, owing to the fact that they are easier to spot. However, since 2005, hundreds of potentially terrestrial extrasolar planets have been found – mainly by the Kepler space mission. Most of these have been what is known as “super-Earths” (i.e. planets with masses between Earth’s and Neptune’s).
Examples of extrasolar terrestrial planets include Gliese 876 d, a planet that has a mass 7 to 9 times that of Earth. This planet orbits the red dwarf Gliese 876, which is located approximately 15 light years from Earth. The existence of three (or possibly four) terrestrial exoplanets was also confirmed between 2007 and 2010 in the Gliese 581 system, another red dwarf roughly 20 light years from Earth.
The smallest of these, Gliese 581 e, is only about 1.9 Earth masses, but orbits very close to the star. Two others, Gliese 581 c and Gliese 581 d, as well as a proposed fourth planet (Gliese 581 g) are more-massive super-Earths orbiting in or close to the habitable zone of the star. If true, this could mean that these worlds are potentially habitable Earth-like planets.
The first confirmed terrestrial exoplanet, Kepler-10b – a planet with between 3 and 4 Earth masses and located some 460 light years from Earth – was found in 2011 by the Kepler space mission. In that same year, the Kepler Space Observatory team released a list of 1235 extrasolar planet candidates, including six that were “Earth-size” or “super-Earth-size” (i.e. less than 2 Earth radii) and which were located within their stars’ habitable zones.
Since then, Kepler has discovered hundreds of planets ranging from Moon-sized to super-Earths, with many more candidates in this size range. As of January, 2013, 2740 planet candidates have been discovered.
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Scientists have proposed several categories for classifying terrestrial planets. Silicate planets are the standard type of terrestrial planet seen in the Solar System, which are composed primarily of a silicon-based rocky mantle and a metallic (iron) core.
Iron planets are a theoretical type of terrestrial planet that consists almost entirely of iron and therefore has a greater density and a smaller radius than other terrestrial planets of comparable mass. Planets of this type are believed to form in the high-temperature regions close to a star, and where the protoplanetary disk is rich in iron. Mercury is possible example, which formed close to our Sun and has a metallic core equal to 60–70% of its planetary mass.
Coreless planets are another theoretical type of terrestrial planet, one that consists of silicate rock but has no metallic core. In other words, coreless planets are the opposite of an iron planet. Coreless planets are believed to form farther from the star where volatile oxidizing material is more common. Though the Solar System has no coreless planets, chondrite asteroids and meteorites are common.
And then there are Carbon planets (aka. “diamond planets”), a theoretical class of planets that are composed of a metal core surrounded by primarily carbon-based minerals. Again, the Solar System has no planets that fit this description, but has an abundance of carbonaceous asteroids.
Until recently, everything scientists knew about planets – which included how they form and the different types that exist – came from studying our own Solar System. But with the explosion that has taken place in exoplanet discovery in the past decade, what we know about planets has grown significantly.
For one, we have come to understand that the size and scale of planets is greater than previously thought. What’s more, we’ve seen for the first time that many planets similar to Earth (which could also include being habitable) do in fact exist in other Solar Systems.
Who knows what we will find once we have the option of sending probes and manned missions to other terrestrial planets?
Astronomy Cast has episodes on the terrestrial planets including Mars, and an interview with Darin Ragozzine, one of the Kepler Space Mission scientists.
Venus and Jupiter at dusk over Australia's Outback on June 27, 2015. Credit: Joseph Brimacombe
The year’s finest conjunction is upon us. Chances are you’ve been watching Venus and Jupiter at dusk for some time.
Like two lovers in a long courtship, they’ve been slowly approaching one another for the past several months and will finally reach their minimum separation of just over 1/4° (half a Full Moon diameter) Tuesday evening June 30.
The view facing west-northwest about 50 minutes after sunset on June 30 when Venus and Jupiter will be at their closest. If bad weather moves in, they’ll be nearly as close tonight (June 29) and July 1. Two celestial bodies are said to be in conjunction when they have the same right ascension or “longitude”and line up one atop the other. Source: Stellarium
Most of us thrill to see a single bright planet let alone the two brightest so close together. That’s what makes this a very special conjunction. Conjunctions are actually fairly common with a dozen or more planet-to-planet events a year and 7 or 8 Moon-planet match-ups a month. It’s easy to see why.
From our perspective in the relatively flat plane of the Solar System we watch the planets cycle around the Sun projected against the backdrop of the zodiac constellations. They – and the Moon – follow the ecliptic and occasionally pass one another in the sky to make for wonderful conjunctions. Credit: Bob King
All eight planets travel the same celestial highway around the sky called the ecliptic but at different rates depending upon their distance from the Sun. Distant Saturn and Neptune travel more slowly than closer-in planets like Mercury and Mars. Over time, we see them lap one another in the sky, pairing up for a week or so and inspiring the gaze of those lucky enough to look up. After these brief trysts, the worlds part ways and move on to future engagements.
Venus and Jupiter above St. Peter’s Dome in Rome on Sunday June 28, 2015. Details: Canon 7D Mark II DSLR, with a 17-55-f/2.8 lens at 24mm f/4 and exposure time was 1/40″. Credit: Gianluca Masi
In many conjunctions, the planets or the Moon and planet are relatively far apart. They may catch the eye but aren’t exactly jaw-dropping events. The most striking conjunctions involve close pairings of the brightest planets. Occasionally, the Moon joins the fray, intensifying the beauty of the scene even more.
As Venus orbits interior to Earth’s orbit, its apparent distance from the Sun (and phase) changes. Since June 6, the planet’s separation from the Sun in the sky has been shrinking and will reach a minimum on August 15, when the planet is directly between the Sun and Earth. Credit: Bob King
While moving planets are behind many conjunctions, they often don’t do it alone. Earth’s orbital motion around the Sun helps move things along. This week’s event is a perfect example. Venus is currently moving away from Jupiter in the sky but not quickly enough to avoid the encounter. Each night, its apparent distance from the Sun decreases by small increments and the planet loses altitude. Meanwhile, Jupiter’s moving away from Venus, traveling east toward Regulus as it orbits around the Sun.
So how can they possibly get together? Earth to the rescue! Every day, our planet travels some 1.6 million miles in our orbit, completing 584 million miles in one year. We see this movement reflected in the rising and setting times of the stars and planets.
View of Earth’s orbit seen from above the northern hemisphere. As our planet moves to the left or counterclockwise around the Sun, the background constellations appear to drift to the right or westward. This causes constellations and planets in the western sky to gradually drop lower every night, while those in the east rise higher. Credit: Bob King
Every night, the stars rise four minutes earlier than the night before. Over days and weeks, the minutes accumulate into hours. When stars rise earlier in the east, those in the west set earlier. In time, all stars and planets drift westward due to Earth’s revolution around the Sun.
It’s this seasonal drift that “pushes” Jupiter westward to eventually overtake a reluctant Venus. Despite appearances, in this particular conjunction, both planets are really fleeing one another!
Johannes Kepler’s depiction of the conjunction of Mercury (left), Jupiter and Saturn shortly before Christmas in the year 1603. He believed a similar conjunction or series of conjunctions – the Christmas Star – may have heralded the birth of Christ.
We’re attuned to unusual planetary groupings just as our ancestors were. While they might have seen a planetary alignment as a portent of kingly succession or ill fortune in battle, we’re free to appreciate them for their sheer beauty. Not to say that some might still read a message or experience a personal revelation at the sight. There’s something in us that sees special meaning in celestial alignments. We’re good at sensing change in our environment, so we sit up and take notice when unusual sky events occur like eclipses, bright comets and close pairings of the Moon and planets.
Venus and Jupiter over the next few nights facing west at dusk. Times and separations shown for central North America at 10 p.m. CDT. 30 minutes of arc or 30′ equals one Full Moon diameter. Source: Stellarium
You can watch the Jupiter-Venus conjunction several different ways. Naked eye of course is easiest. Just face west starting about an hour after sunset and drink it in. My mom, who’s almost 90, will be watching from her front step. Binoculars will add extra brilliance to the sight and perhaps show several moons of Jupiter.
The view through a small telescope of Jupiter (top) and Venus on June 30 around 9:30 p.m. CDT. Jupiter’s moons are G = Ganymede, E = Europa, I = Io and C = Callisto. Source: Stellarium
If you have a telescope, I encourage you to point it at the planetary doublet. Even a small scope will let you see Jupiter’s two dark, horizontal stripes — the North and South Equatorial Belts — and several moons. Venus will appear as a pure white, thick crescent 32 arc seconds across virtually identical in apparent size to Jupiter. To tame Venus’ glare, start observing early when the sky is still flush with pale blue twilight. I think the best part will be seeing both planets in the same field of view even at moderate magnification — a rare sight!
To capture an image of these shiny baubles try using your cellphone. For many, that’s the only camera we have. First, find a pretty scene to frame the pair. Hold your phone rock-solid steady against a post or building and click away starting about an hour after sundown when the two planets have good contrast with the sky, but with light still about. If your pictures appear too dark or light, manually adjust the exposure. Here’s a youtube video on how to do it with an iPhone.
Jupiter and Venus at dusk on June 26. This is a 6-second exposure at f/2.8 and ISO 80 taken with a basic point-and-shoot digital camera. I braced the camera on top of a mailbox and stuck my phone underneath to prop up the lens. Credit: Bob King
Point-and-shoot camera owners should place their camera on a tripod, adjust the ISO or sensitivity to 100, open the aperture or f/stop to its widest setting (f/2.8 or f/4), autofocus on the planets and expose from 5-10 seconds in mid-twilight or about 1 hour to 90 minutes after sunset. The low ISO is necessary to keep the images from turning grainy. High-end digital SLR cameras have no such limitations and can be used at ISO 1600 or higher. As always, review the back screen to make sure you’re exposing properly.
I’m not a harmonic convergence kind of guy, but I believe this week’s grand conjunction, visible from so many places on Earth, will stir a few souls and help us appreciate this life that much more.
The symbols of the eight planets, and Pluto, Credit: insightastrology.net
In our long history of staring up at the stars, human beings have assigned various qualities, names, and symbols for all the objects they have found there. Determined to find patterns in the heavens that might shed light on life here on Earth, many of these designations also ascribed (and were based on) the observable behavior of the celestial bodies.
When it came to assigning signs to the planets, astrologists and astronomers – which were entwined disciplines in the past -made sure that these particular symbols were linked to the planets’ names or their history in some way.
Mercury:
This planet is named after the Roman god who was himself the messenger of the gods, noted for his speed and swiftness. The name was assigned to this body largely because it is the planet closest to the Sun, and which therefore has the fastest rotational period. Hence, the symbol is meant to represent Mercury’s helmet and caduceus – a herald’s staff with snakes and wings intertwined.
Mercury, as imaged by the MESSENGER spacecraft, which was named after the messenger of the gods because it has the fastest orbit around the Sun. Image Credit: NASA/JHU/Carnegie Institution.
Venus:
Venus’ symbol has more than one meaning. Not only is it the sign for “female”, but it also represents the goddess Venus’ hand mirror. This representation of femininity makes sense considering Venus was the goddess of love and beauty in the Roman Pantheon. The symbol is also the chemical sign for copper; since copper was used to make mirrors in ancient times.
Earth:
Earth’s sign also has a variety of meanings, although it does not refer to a mythological god. The most popular view is that the circle with a cross in the middle represents the four main compass points. It has also been interpreted as the Globus Cruciger, an old Christian symbol for Christ’s reign on Earth.
This symbol is not just limited to Christianity though, and has been used in various culture around the world. These include, but are not limited to, Norse mythology (where it appears as the Solar or Odin’s Cross), Native American cultures (where it typically represented the four spirits of direction and the four sacred elements), the Celtic Cross, the Greek Cross, and the Egyptian Ankh.
In fact, perhaps owing to the simplicity of the design, cross-shaped incisions have made appearances as petroglyphs in European cult caves dating all the way back to the beginning of the Upper Paleolithic, and throughout prehistory to the Iron Age.
Mars, as photographed with the Mars Global Surveyor, is identified with the Roman god of war. Credit: NASA
Mars:
Mars is named after the Roman god of war, owing perhaps to the planet’s reddish hue, which gives it the color of blood. For this reason, the symbol associated with Mars represents the god of wars’ shield and spear. Additionally, it is the same sign as the one used to represent “male”, and hence is associated with self-assertion, aggression, sexuality, energy, strength, ambition and impulsiveness.
Jupiter:
Jupiter’s sign, which looks like an ornate, oddly shaped “four,” also stands for a number of symbols. It has been said to represent an eagle, which was the Jovian god’s bird. Additionally, the symbol can stand for a “Z,” which is the first letter of Zeus – who was Jupiter’s Greek counterpart.
The line through the symbol is consistent with this, since it would indicate that it was an abbreviation for Zeus’ name. And last, but not least, there is the addition of the swirled line which is believed to represent a lighting bolt – which just happens to Jupiter’s (and Zeus’) weapon of choice.
Saturn:
Like Jupiter, Saturn resembles another recognizable character – this time, it’s an “h.” However, this symbol is actually supposed to represent Saturn’s scythe or sickle, because Saturn is named after the Roman god of agriculture (after the Greek god Cronus, leader of the Titans, who was also depicted as holding a scythe).
Jupiter, the largest planet in the Solar System, is appropriately named after the Roman father of the gods. Credit: NASA/ESA/A. Simon (Goddard Space Flight Center)
Uranus:
The sign for Uranus is a combination of two other signs – Mars’ sign and the symbol of the Sun – because the planet is connected to these two in mythology. Uranus represented heaven in Roman mythology, and this ancient civilization believed that the Sun’s light and Mars’ power ruled the heavens.
Neptune:
Neptune’s sign is linked to the sea god Neptune, who the planet was named after. Appropriately, the symbol represents this planet is in the shape of the sea god’s trident.
Pluto:
Although Pluto was demoted to a dwarf planet in 2006, it still retains its old symbol. Pluto’s sign is a combination of a “P” and a “L,” which are the first two letters in Pluto as well as the initials of Percival Lowell, the astronomer who discovered the planet.
A full Moon flyby, as seen from Paris, France. Credit and copyright: Sebastien Lebrigand.
Moon:
The Moon is represented by a crescent shape, which is a clear allusion to how the Moon appears in the night sky more often than not. Since the Moon is also tied to people’s perceptions, moods, and emotional make-up, the symbol has also come to represents the mind’s receptivity.
Sun:
And then there’s the Sun, which is represented by a circle with a dot in the middle. In the case of the Sun, this symbol represents the divine spirit (circle) surrounding the seed of potential, which is a direct association with ancient Sun worship and the central role the Sun gods played in their respective ancient pantheons.
When humans finally travel into space, where will we live? Will we ever be able to colonize gas giants like Jupiter?
NASA and Elon Musk have plans to get your ass to Mars.
It’s not impossible to imagine humans living and working on the Red Planet. Maybe they’ll be crusty asteroid miners making their fortune digging precious minerals out of the inexhaustible supply of space rocks. Pray they don’t dig too deeply. We should go ask Kuato, that creepy little guy knows everything! Except he’s always trying to get you to touch his funny little hands. Pass.
Venus looks like it’s a pretty great place to live, if we stick to the clouds in floating sky cities, plying the jet streams in our steampunk dirigibles. It’ll be fun, but first, does anyone know how to attach a cog to a top hat? Venus, here we come!
We should stay away from the surface, though, that place’ll kill you dead. We’re guessing a crispy shell holding in a gooey center, at least for the first few moments. Once we sort the living in space deal, is there anywhere we won’t be able to go?
We could create underwater cities on Europa or Ganymede, in the vast oceans with the exotic hopefully unarmed, peaceful, vegetarian Jovian whales.Like Jupiter? Could we live there?
Jupiter is the most massive planet in the Solar System. It has a diameter of almost 140,000 kilometers and it’s made mostly of hydrogen and helium; the same materials of the Sun. It has more than 317 times the mass of the Earth, providing its enormous gravity.
If you could stand on the cloud tops of Jupiter, you would experience 2.5 times the gravity that you experience on Earth. Then you’d fall to your death, because it’s a gas planet, made of hydrogen, the lightest element in the Universe. You can’t stand on gas, rookie.
If you tried to bring your Venusian Vernian exploratorium ballooncraft for a jaunt across the skies of Jupiter, it would sink like a copper bowler with lead goggles.
The only thing that’s lighter than hydrogen is hot hydrogen. Let’s say you could make a balloon, and fill it with superheated hydrogen and float around the cloud tops of Jupiter suffering the crushing gravity. Is there anything else that might kill you?
Did you leave Earth? Then of course there is. Everything is going to kill you, always. You might want to write that on the brass plaque next to your ship’s wheel with the carving of Shiva in the center there, Captain Baron Cogsworth Copperglass.
Jupiter’s Great Red Spot and Ganymede’s Shadow. Image Credit: NASA/ESA/A. Simon (Goddard Space Flight Center)
Jupiter is surrounded by an enormous magnetic field, ten times more powerful than Earth’s. It traps particles and then whips them around like an accelerator. This radiation is a million times more powerful than the Earth’s Van Allen belts. Our big human meat roasting concern during the Apollo days.
If you tried to get near the radiation belts without insufficient shielding. It’d be bad. Just picture jamming your copper and brass steamwork fantasy into a giant microwave.
Is it possible there’s a solid core, deep down within Jupiter? Somewhere we could live, and not have to worry about those pesky buoyancy problems? Probably. Astronomers think there are a few times the mass of the Earth in rocky material deep down inside.
Of course, the pressure and temperature are incomprehensible. The temperature at the core of Jupiter is thought to be 24,000 degrees Celsius. Hydrogen is crushed so tightly it becomes superheated liquid or strange new flavors of ice. It becomes a metal.
The moral, we’re not equipped to go there. Let alone set up shop. So, let’s just stick with fantasizing your adventures as Emperor Esquire Beardweirdy Brassnozzle Steamypantaloons.
In his classic book 2001, Arthur C. Clarke said that “all these worlds are yours except Europa, attempt no landing there”. Well that’s crazy.
Europa’s awesome, we’re totally landing there, especially if we discover alien whales. So, Europa first. Besides, it’s just a book. So, Jupiter is the worst. Do not navigate your airship into that harbour.
What’s the worst possible environment you can imagine to try and live on? Tell us in the comments below.
