Astronomy Archives

July 26, 2016February 14, 2017 by Matt Williams

How Far is Mars from the Sun?

The eccentricity in Mars' orbit means that it is . Credit: NASA

With the Scientific Revolution, astronomers became aware of the fact that the Earth and the other planets orbit the Sun. And thanks to Copernicus, Galileo, Kepler, and Newton, the study of their orbits was refined to the point of mathematical precision. And with the subsequent discoveries of Uranus, Neptune, Pluto and the Kuiper Belt Objects, we have come to understand just how varied the orbits of the Solar Planets are.

Consider Mars, Earth’s second-closest neighbor, and a planet that is often referred to as “Earth’s Twin”. While it has many things in common with Earth, one area in which they differ greatly is in terms of their orbits. In addition to being farther from the Sun, Mars also has a much more elliptical orbit, which results in some rather interesting variations in temperature and weather patterns.

Perihelion and Aphelion:

Mars orbits the Sun at an average distance (semi-major axis) of 228 million km (141.67 million mi), or 1.524 astronomical units (over one and a half times the distance between Earth and the Sun). However, Mars also has the second most eccentric orbit of all the planets in the Solar System (0.0934), which makes it a distant second to crazy Mercury (at 0.20563).

This means that Mars’ distance from the Sun varies between perihelion (its closest point) and aphelion (its farthest point). In short, the distance between Mars and the Sun ranges during the course of a Martian year from 206,700,000 km (128.437 million mi) at perihelion and 249,200,000 km (154.8457 million mi) at aphelion – or 1.38 AU and 1.666 AU.

Speaking of a Martian year, with an average orbital speed of 24 km/s, Mars takes the equivalent of 687 Earth days to complete a single orbit around the Sun. This means that a year on Mars is equivalent to 1.88 Earth years. Adjusted for Martian days (aka. sols) – which last 24 hours, 39 minutes, and 35 seconds – that works out to a year being 668.5991 sols long (still almost twice as long).

Mars in also the midst of a long-term increase in eccentricity. Roughly 19,000 years ago, it reached a minimum of 0.079, and will peak again at an eccentricity of 0.105 (with a perihelion distance of 1.3621 AU) in about 24,000 years. In addition, the orbit was nearly circular about 1.35 million years ago, and will be again one million years from now.

Axial Tilt:

Much like Earth, Mars also has a significantly tilted axis. In fact, with an inclination of 25.19° to its orbital plane, it is very close to Earth’s own tilt of 23.439°. This means that like Earth, Mars also experiences seasonal variations in terms of temperature. On average, the surface temperature of Mars is much colder than what we experience here on Earth, but the variation is largely the same.

. Credit and copyright: Encyclopedia Britannica — *Mars eccentric orbit and axial tilt result in considerable seasonal variations. Credit and Copyright: Encyclopedia Britannica*

All told, the average surface temperature on Mars is -46 °C (-51 °F). This ranges from a low of -143 °C (-225.4 °F), which takes place during winter at the poles; and a high of 35 °C (95 °F), which occurs during summer and midday at the equator. This means that at certain times of the year, Mars is actually warmer than certain parts of Earth.

Orbit and Seasonal Changes:

Mars’ variations in temperature and its seasonal changes are also related to changes in the planet’s orbit. Essentially, Mars’ eccentric orbit means that it travels more slowly around the Sun when it is further from it, and more quickly when it is closer (as stated in Kepler’s Three Laws of Planetary Motion).

Mars’ aphelion coincides with Spring in its northern hemisphere, which makes it the longest season on the planet – lasting roughly 7 Earth months. Summer is second longest, lasting six months, while Fall and Winter last 5.3 and just over 4 months, respectively. In the south, the length of the seasons is only slightly different.

Mars is near perihelion when it is summer in the southern hemisphere and winter in the north, and near aphelion when it is winter in the southern hemisphere and summer in the north. As a result, the seasons in the southern hemisphere are more extreme and the seasons in the northern are milder. The summer temperatures in the south can be up to 30 K (30 °C; 54 °F) warmer than the equivalent summer temperatures in the north.

Mars' south polar ice cap, seen in April 2000 by Mars Odyssey. NASA/JPL/MSSS — *Mars’ south polar ice cap, seen in April 2000 by the Mars Odyssey probe. Credit: NASA/JPL/MSSS*

It also snows on Mars. In 2008, NASA’s Phoenix Lander found water ice in the polar regions of the planet. This was an expected finding, but scientists were not prepared to observe snow falling from clouds. The snow, combined with soil chemistry experiments, led scientists to believe that the landing site had a wetter and warmer climate in the past.

And then in 2012, data obtained by the Mars Reconnaissance Orbiter revealed that carbon-dioxide snowfalls occur in the southern polar region of Mars. For decades, scientists have known that carbon-dioxide ice is a permanent part of Mars’ seasonal cycle and exists in the southern polar caps. But this was the first time that such a phenomena was detected, and it remains the only known example of carbon-dioxide snow falling anywhere in our solar system.

In addition, recent surveys conducted by the Mars Reconnaissance Orbiter, the Mars Science Laboratory, the Mars Orbiter Mission (MOM), the Mars Atmosphere and Volatile Evolution (MAVEN) and the Opportunity and Curiosity Rovers have revealed some startling things about Mars’ deep past.

For starters, soil samples and orbital observation have demonstrated conclusively that roughly 3.7 billion years ago, the planet had more water on its surface than is currently in the Atlantic Ocean. Similarly, atmospheric studies conducted on the surface and from space have proven that Mars also had a viable atmosphere at that time, one which was slowly stripped away by solar wind.

*Scientists were able to gauge the rate of water loss on Mars by measuring the ratio of water and HDO from today and 4.3 billion years ago. Credit: Kevin Gill*

Weather Patterns:

These seasonal variations allow Mars to experience some extremes in weather. Most notably, Mars has the largest dust storms in the Solar System. These can vary from a storm over a small area to gigantic storms (thousands of km in diameter) that cover the entire planet and obscure the surface from view. They tend to occur when Mars is closest to the Sun, and have been shown to increase the global temperature.

The first mission to notice this was the Mariner 9 orbiter, which was the first spacecraft to orbit Mars in 1971, it sent pictures back to Earth of a world consumed in haze. The entire planet was covered by a dust storm so massive that only Olympus Mons, the giant Martian volcano that measures 24 km high, could be seen above the clouds. This storm lasted for a full month, and delayed Mariner 9‘s attempts to photograph the planet in detail.

And then on June 9th, 2001, the Hubble Space Telescope spotted a dust storm in the Hellas Basin on Mars. By July, the storm had died down, but then grew again to become the largest storm in 25 years. So big was the storm that amateur astronomers using small telescopes were able to see it from Earth. And the cloud raised the temperature of the frigid Martian atmosphere by a stunning 30° Celsius.

These storms tend to occur when Mars is closest to the Sun, and are the result of temperatures rising and triggering changes in the air and soil. As the soil dries, it becomes more easily picked up by air currents, which are caused by pressure changes due to increased heat. The dust storms cause temperatures to rise even further, leading to Mars’ experiencing its own greenhouse effect.

We have written many interesting articles about the distance of the planets from the Sun here at Universe Today. Here’s How Far Are the Planets from the Sun?, How Far is Mercury from the Sun?, How Far is Venus from the Sun?, How Far is the Earth from the Sun?, How Far is the Moon from the Sun?, How Far is Jupiter from the Sun?, How Far is Saturn from the Sun?, What is Uranus’ Distance from the Sun?, What is the Distance of Neptune from the Sun? and How Far is Pluto from the Sun?

For more information, Astronomy for beginners teaches you how to calculate the distance to Mars.

Finally, if you’d like to learn more about Mars in general, we have done several podcast episodes about the Red Planet at Astronomy Cast. Episode 52: Mars, and Episode 91: The Search for Water on Mars.

July 26, 2016 by David Dickinson

Celestial Photobomb: Rare Occultation of Mercury by the Moon Set for Next Week

Mercury and the Moon over the ramparts of Assilah, Morocco. Photo by author

Have you caught sight of Mercury yet? This coming week is a good time to try, looking low to the west at dusk. We just managed to to nab it with binoculars for the first time during the current apparition this past Sunday from the rooftop of our Air BnB in Casablanca, Morocco.

Mercury is a tough grab under any circumstance, that’s for sure. Brilliant Venus and Jupiter make great guides to finding the elusive planet in late July, as it ping-pongs between the two. The waxing crescent Moon joins the scene in the first week of August, and for a very lucky few, actually occults (passes in front of ) the diminutive innermost world shortly after passing New.

Mercury (arrowed) near the Moon on the morning of June 3rd, 2016. Image credit: Dave Dickinson.

Here’s the low down on everything Mercurial, and circumstances for the coming weeks.

Mercury passes 18′ from the star Regulus on Saturday, July 30^th at 19:00 Universal Time (UT), representing the closest passage of a planet near a first magnitude star for 2016.

The Moon then reaches New phase, marking the start of lunation 1158 on August 2^nd at 20:45 UT. The Moon then moves on to occult Mercury on Thursday, August 4^th at 22:00 UT, just over 48 hours later. The occultation is visible at dusk for observers based in southern Chile and southern Argentina. The rest of us see a close pass. Note that although it is a miss for North America, viewers based on the continent share the same colongitude and will see Mercury only a degree off of the northern limb of the Moon on the night of August 4^th. Mercury shines at magnitude +0.01, and presents a 67% illuminated disk 6.3” in size, while the Moon is a slender 5% illuminated.

Occultations of Mercury for 2016. Credit: Occult 4.2. (click image to enlarge).

How early can you see the waxing crescent Moon? Catching the Moon with the naked eye under transparent clear skies isn’t usually difficult when it passes 20 hours old. This cycle, first sightings favor South Africa westward on the night of August 3^rd.

Mercury reaches greatest elongation 27.4 degrees east of the Sun 12 days after this occultation on August 16^th.

How rare is it? Well occultations of Mercury by the Moon are the toughest to catch of all the naked eye planets, owing to the fact that the planet never strays far from the Sun. Nearly all of these events go unwitnessed, as they occur mainly under daytime skies. And while you can observe Mercury in the daytime near greatest elongation with a telescope, safety precautions need to be taken to assure the Sun is physically blocked from view. Astronomers of yore did exactly that, hoping to glimpse fleeting detail on Mercury while it was perched higher in the sky above the murk of the atmosphere low to the horizon.

In fact, a quick search of ye ole web reveals very few convincing captures of an occultation of Mercury (see the video above). The closest grab thus far comes from astrophotographer Cory Schmitz on June 3^rd 2016 based in South Africa:

Image credit: — Can you see it? The Moon about to occult Mercury on June 3rd. Image credit and copyright: Cory Schmitz.

Can’t wait til next week? The Moon crosses the Hyades open star cluster this week, occulting several stars along the way. The action occurs on the morning of Friday, July 29^th culminating with an occultation of +1 magnitude Aldebaran by the 23% illuminated Moon. Texas and Mexico are well-placed to see this event under dark skies. A small confession: we actually prefer occultations of planets and stars by the waxing Moon, as the dark edge of the Moon is leading during ingress, making it much easier to witness and the exact moment the Moon blots out the object.

Still want more? The Moon actually goes on to occult Jupiter on August 6^th for the South Pacific. Viewers farther west in southeast Asia might just spy this one in the daytime. This is the second occultation of Jupiter by the Moon in a series of four in 2016.

Looking west on the evening of August 4th. Image credit: Stellarium.

Keep and eye on those planets in August, as they’re now all currently visible in the dusk sky. The Moon, Regulus and Venus also form a tight five degree triangle on the evening of August 4^th, followed by a slightly wider grouping of Venus, Jupiter and the Moon around August 25^th.

More to come on that soon. Be sure to check the planet Mercury off of your life list this coming week, using the nearby waxing crescent Moon as a guide.

July 25, 2016July 25, 2016 by Matt Williams

Groot & Rocket Raccoon Get Their Own Mission Patch

For the remainder of 2016, all payloads traveling to the US National Lab aboard the ISS will feature a mission patch with Marvel characters. Credit: NASA

In 2011, the US government created the Center for the Advancement of Science in Space (CASIS) to manage the US National Laboratory aboard the International Space Station,. With the purpose of ensuring that research opportunities provided by the ISS are used to their full potential, CASIS also seeks to inspire new generations of students to become involved in STEMs research and space exploration.

With the next generation in mind, CASIS recently announced the creation of a new mission patch that is sure to appeal to sci-fi fans and space enthusiasts! The patch features Groot and Rocket Raccoon, two characters from the Guardians of the Galaxy franchise, and was designed by Marvel Comic’s Custom Solution Group. For the remainder of 2016, it will represent all payloads that are destined for the ISS’ US National Laboratory.

The announcement came at the 2016 San Diego Comic Con, where tens of thousands of fans were gathered to witness the latest from their favorite sci-fi, fantasy, and comic book franchises. In between all the trailers and fanfare, members of CASIS held a panel discussion to talk about their collaboration with Marvel, and explained why it was these two Guardians characters that were selected to promote activities aboard the ISS.

*This mission patch, featuring Groot and Rocket Racoon, will adorn all cargo going to CASIS labs in 2016. Credit: iss-casis.org*

As Patrick O’Neill, a representative of CASIS, was quoted by The Verge as saying: “These are characters who have a bit of a space-based background to begin with. So both of [these] characters already embody some of the characteristics associated with what’s happening on the space station.”

The patch – which was designed by famed Marvel artist “Juan Doe” – features Groot and Rocket Racoon staring up at the ISS, which is floating overhead. In and around them, stars that are made to look like the flames from the Guardian of the Galaxy shield are positioned. In addition to being artistically creative, the symbolism could not be more clear: pop-culture icons and the ISS National Lab coming together to raise awareness about important scientific research!

During 2016, the U.S. National Lab plans to conduct over 100 science investigations aboard the ISS, with experiments involving the physical and material sciences, technological development, Earth observation and student inquiries. Thanks to its partnership with Marvel, the Guardians-inspired patch will adorn every payload that is sent to the ISS as part of these research initiatives.

Obviously, this partnership has been a good way for Marvel to promote one of the latest installments in its cinematic universe (not to mention its upcoming sequel). But for CASIS, it was also an opportunity to draw attention to the work of the U.S. National Lab. Traditionally, CASIS is responsible for providing seed money to research projects and product development. But a major aspect of their work also includes providing expertise, access, support, and educational outreach.

*The Center for the Advancement of Science in Space (CASIS), shown here as part of the ISS. Credit: iss-casis.org*

As Ken Shields, the CASIS Director of Operations and Educational Opportunities, said in a CASIS press release:

“A major mission for us here at CASIS is to find unique and innovative ways to bring notoriety to the ISS National Laboratory and the research that is being conducted on our orbiting laboratory. There are very few brands in the world who have as large an impact as Marvel, and we are thrilled to partner with them on this project and look forward to Rocket and Groot inspiring a new generation of researchers interested in the space station.”

Later this year, CASIS also hopes to use these characters in an upcoming educational flight contest intended to inspire children to become the next generation of scientists and engineers. News of the mission patch also came amidst announcements that Rocket and Groot will be star in their own Rocket Raccoon and Groot comic, and will be returning to the big screen next summer for Guardians of the Galaxy 2.

Obviously, this is going to be a good year for a certain tree alien and hyper-raccoon! And be sure to check out this video of the creation of the new mission patch, courtesy of CASIS:

Further Reading: iss-casis.org

July 25, 2016July 25, 2016 by Tammy Plotner

Messier 20 (M20) – The Trifid Nebula

The Triffid Nebula (on the left), with M21 open star cluster to the right. Credit and Copyright: NASA/Lorand Fenyes

Welcome back to Messier Monday! In our ongoing tribute to the great Tammy Plotner, we take a look at the Trifid Nebula (aka. Messier 20). Enjoy!

Back in the 18th century, famed French astronomer Charles Messier noted the presence of several “nebulous objects” in the night sky. Having originally mistaken them for comets, he began compiling a list of these objects so that others wouldn’t make the same mistake. Consisting of 100 objects, the Messier Catalog would come to be viewed by posterity as a major milestone in the study of Deep Space Objects.

One of these objects is the Trifid Nebula (aka. Messier 20, NGC 6514), a star-forming region of ionized gas located in the Scutum spiral arm of the Milky Way, in the direction of the southern Sagittarius constellation. A bright object that is a favorite amongst amateur astronomers, this object is so-named because it is a combination open star cluster, emissions nebula, reflection nebula, and a dark nebula that looks like it consists of three lobes.

Description:

Almost everyone who is familiar with space images has likely seen a beautiful color image of this emission and reflection nebula. However, when looking at M20 through a telescope, what you will see will be less colorful. Why? When it comes to photographs, exposure times and wavelengths cause different colors to become visible.

Composite image comparing visible-light views from Hubble of the Trifid Nebula with an infrared view from NASA’s Spitzer Space Telescope of the glowing Trifid Nebula. Credit: NASA/JPL-Caltech/J. Rho (SSC/Caltech)

Photographically, the red emission nebula contained within Messier 20 has a bright blue star cluster in it central portion. It glows red because the ultraviolet light of the stars ionizes the hydrogen gas, which then recombines and emits the characteristic red hydrogen-alpha light captured on film. Further away, the radiation from these hot, young stars becomes too weak to ionize the hydrogen. Now the gas and dust glows blue by reflection!

No matter how it is observed, the Trifid – or “three lobed” – nebula has a distinctive set of dark dust lanes which divide it. These also have a classification of their own, and were cataloged by E.E. Barnard as a dark nebula – Barnard 85 (B 85). In 1999 the Hubble Space Telescope took a look deep into the Trifid nebula at some of its star forming regions (see below).

What it found was a stellar jet poking its way into the cloud, like a fabulous twisted antenna. Inside the exhaust column is a new star waiting to be born, yet sometime over the next 10,000 years the central massive star will probably erode away all of its material before it can fully form. Nearby, a stalk stands waiting.

Close up on the interiotr of the Trifid Nebula. Credit: NASA/HST — *Close up on the interior of the Trifid Nebula, showing the star forming region and a stellar jet. Credit: NASA/HST*

Like the jet, it is also a stellar nursery – one with an EGG (evaporating gaseous globule) at its tip – a condensed cloud of gas able to survive so far. As Jeff Hester of the Department of Physics & Astronomy explained:

“If our interpretation is correct, the microjet may be the last gasp from a star that was cut off from its supply lines 100,000 years ago. The vast majority of stars like our sun form not in isolation, but in the neighborhood of massive, powerful stars. HST observations of the Trifid Nebula provide a window on the nature of star formation in the vicinity of massive stars, as well as a spectacular snapshot of the “ecology” from which stars like our sun emerge.”

We know that Messier 20 contains new stars, but what about old stars? Are there surprises buried within these bright folds that still await discovery? According to F. Yusef-Zadeh (et al) and a 2000 study titled “Radio continuum emission from the central stars of M20 and the detection of a new supernova remnant near M20“, the answer is yes:

“We report the discovery of a new candidate barrel-shaped supernova remnant (SNR) lying adjacent to M20 and two shell-type features to the north and east of SNR W28. Future observations should clarify whether the nonthermal shell fragment is either part of W20 or yet another previously unidentified shell-type SNR.”

The Trifid nebula (M20, NGC NGC 6514) in pseudocolor. Image taken with the Palomar 1.5-m telescope. The field of view is 16’ ´ 16’. Red shows [S II] ll 6717+6731. Green shows Ha l 6563. Blue shows [O III] l 5007. The WFPC2 field of view is indicated. Image: Jeff Hester (Arizona State University), Palomar telescope. — *The Trifid nebula (M20, NGC NGC 6514) in pseudocolor. Image taken with the Palomar 1.5-m telescope. Credit: Jeff Hester (Arizona State University)/Palomar telescope*

History of Observation:

Charles Messier discovered this object on June 5th, 1764. As he recorded of the object in his notes:

“In the same night I have determined the position of two clusters of stars which are close to each other, a bit above the Ecliptic, between the bow of Sagittarius and the right foot of Ophiuchus: the known star closest to these two clusters is the 11th of the constellation Sagittarius, of seventh magnitude, after the catalog of Flamsteed: the stars of these clusters are, from the eighth to the ninth magnitude, environed with nebulosities. I have determined their positions. The right ascension of the first cluster, 267d 4′ 5″, its declination 22d 59′ 10″ south. The right ascension of the second, 267d 31′ 35″; its declination, 22d 31′ 25″ south.”

While Messier did separate the two star clusters, he did not note so many different portions to the nebula – but, he did note nebulosity. In this circumstance, we cannot fault him. His purpose was to locate comets, after all; and the reason for the catalog was to list objects that were not. In later years, it would be Sir William Herschel who would take a closer look at Messier 20 and discover much more. As he wrote of the nebula:

“If it was supposed that double nebulae at some distance from each other would frequently be seen, it will now on the contrary be admitted that an expectation of finding a great number of attracting centers in a nebulosity of no great extent is not so probable; and accordingly observation has shewn that greater combinations of nebular than those of the foregoing article are less frequently to be seen. The following list however contains 20 treble, 5 quadruple, and 1 sextuple nebulae of this sort. Among the treble nebulae there is one, namely H V.10 [M20], of which the nebulosity is not yet separated. Three nebulae seem to join faintly together, forming a kind of triangle; the middle of which is less nebulous, or perhaps free of nebulosity; in the middle of the triangle is a double star of the 2nd or 3rd class; more faint nebulosities are following.”

A close detail of the Trifid Nebula, showing the "Pillar region". Credit: NASA and Jeff Hester (Arizona State University). — *A close detail of the Trifid Nebula, showing a “Pillar” region. Credit: NASA/Jeff Hester (Arizona State University).*

While William went on to catalog four separate areas in his books, it was his son John to whom we owe the famous name that we know it by today. “A most remarkable object. Very large; trifid, three nebulae with a vacuity in the midst, in which is centrally situated the double star Sh 379, the nebula is 7′ in extent. A most remarkable object.”

Just remember when you observe that sky conditions are everything and that not even a large telescope can make it appear if the sky isn’t right. Even Admiral Smyth has his share of troubles spotting it. Said he of the Trifid Nebula:

“I lowered the telescope a couple of degrees, and gazed for the curious trifid nebula, 41 H. IV [H IV.41]; but though I could make out the delicate triple star in the centre of its opening, the nebulous matter resisted the light of my telescope, so that its presence was only indicated by a peculiar glow. Pretty closely preceding this is No. 20 M., an elegant cruciform group of stars, discovered in 1764, which he considered to be surrounded with nebulosity.”

Locating Messier 20:

Once you have become familiar with the Sagittarius region, finding Messier 20 is easy, since it is located just 2 degrees northwest of Messier 8 – the “Lagoon” Nebula. However, at magnitude 9, it isn’t an easy to spot with small binoculars, and not always easy for a small telescope either. Because we often see it depicted in pictures as bright and beautiful, we simply assume M20 will jump out of the sky; but you’ll find that its a lot fainter and more elusive than you might think.

*The Sagittarius constellation. Credit: iau.org*

If you are a beginner to astronomy, try starting at the teapot’s tip star (Lambda), “Al Nasl”, and starhopping in the finderscope northwest to the Lagoon. While the nebulosity might not show in your finder, the optical double star 7 Sagittari, will. From there you will spot a bright cluster of stars two degrees due north. These are the stars embedded withing the Trifid and the small, compressed area of stars to its northeast is the open star cluster of Messier 21.

Center your finderscope on the north and south oriented pair of stars and observe. Remember that you will need a moonless night and that sky conditions will need to be right to see the dark dustlanes! And here are the quick facts about M20, for your convenience:

Object Name: Messier 20
Alternative Designations: M20, NGC 6514, Trifid Nebula
Object Type: Emission Nebula and Reflection Nebula with Open Star Cluster
Constellation: Sagittarius
Right Ascension: 18 : 02.6 (h:m)
Declination: -23 : 02 (deg:m)
Distance: 5.2 (kly)
Visual Brightness: 9.0 (mag)
Apparent Dimension: 28.0 (arc min)

Good luck and enjoy your observations!

We have written many interesting articles about Messier Objects here at Universe Today. Here’s Tammy Plotner’s Introduction to the Messier Objects, , M1 – The Crab Nebula, M8 – The Lagoon Nebula, and David Dickison’s articles on the 2013 and 2014 Messier Marathons.

Be to sure to check out our complete Messier Catalog. And for more information, check out the SEDS Messier Database.

July 25, 2016January 16, 2018 by Matt Williams

Falcon Heavy Vs. Saturn V

The Saturn V (left) and the Falcon Heavy (right). Credit: NASA/SpaceX

Its an Epic Rocket Battle! Or a Clash of the Titans, if you will. Except that in this case, the titans are the two of the heaviest rockets the world has ever seen. And the contenders couldn’t be better matched. On one side, we have the heaviest rocket to come out of the US during the Space Race, and the one that delivered the Apollo astronauts to the Moon. On the other, we have the heaviest rocket created by the NewSpace industry, and which promises to deliver astronauts to Mars.

And in many respects, the Falcon Heavy is considered to be the successor of the Saturn V. Ever since the latter was retired in 1973, the United States has effectively been without a super-heavy lifter. And with the Space Launch System still in development, the Falcon Heavy is likely to become the workhorse of both private space corporations and space agencies in the coming years.

So let’s compare these two rockets, taking into account their capabilities, specifications, and the history of their development and see who comes out on top. BEGIN!

*Launch of the modified Saturn V rocket carrying the Skylab space station. Credit: NASA*

Development History:

The development of the Saturn V began in 1946 with Operation Paperclip, a US government program which led to the recruitment of Wernher von Braun and several other World War II-era German rocket scientists and technicians. The purpose of this program was to leverage the expertise of these scientists to give the US an edge in the Cold War through the development of intercontinental ballistic missiles (ICBMs).

Between 1945 and the mid-to-late 50s von Braun acted as an advisor to US armed forces for the sake of developing military rockets only. It was not until 1957, with the Soviet launch of Sputnik-1 using an R-7 rocket – a Soviet ICBM also capable of delivering thermonuclear warheads – that the US government began to consider the use of rockets for space exploration.

Thereafter, von Braun and his team began developing the Jupiter series of rockets – a modified Redstone ballistic missile with two solid-propellant upper stages. These proved to be a major step towards the Saturn V, hence why the Jupiter series was later nicknamed “an infant Saturn”. Between 1960 and 1962, the Marshall Space Flight Center began designing the rockets that would eventually be used by the Apollo Program.

After several iterations, the Saturn C-5 design (later named the Saturn V) was created. By 1964, it was selected for NASA’s Apollo Program as the rocket that would conduct a Lunar Orbit Rendezvous (LRO). This plan called for a large rocket to launch a single spacecraft to the Moon, but only a small part of that spacecraft (the Lunar Module) would actually land on the surface. That smaller module would then rendezvous with the main spacecraft – the Command/Service Module (CSM) – in lunar orbit and the crew would return home.

A Saturn IV launching the historic Apollo 11 mission. Image: NASA/Michael Vuijlsteke. Public Domain image. — *A Saturn V launching the historic Apollo 11 mission. Credit: NASA/Michael Vuijlsteke. Public Domain image.*

Development of the Falcon Heavy was first announced in 2011 at the National Press Club in Washington D.C. In a statement, Musk drew direct comparisons to the Saturn V, claiming that the Falcon Heavy would deliver “more payload to orbit or escape velocity than any vehicle in history, apart from the Saturn V moon rocket, which was decommissioned after the Apollo program.”

Consistent with this promise of a “super heavy-lift” vehicle, SpaceX’s original specifications indicated a projected payload of 53,000 kg (117,000 lbs) to Low-Earth Orbit (LEO), and 12,000 kgg (26,000 lbs) to Geosynchronous Transfer Orbit (GTO). In 2013, these estimates were revised to 54,400 kg (119,900 lb) to LEO and 22,200 kg (48,900 lb) to GTO, as well as 16,000 kilograms (35,000 lb) to translunar trajectory, and 13,600 kilograms (31,000 lb) on a trans-Martian orbit to Mars, and 2,900 kg (6,400 lb) to Pluto.

In 2015, the design was changed – alongside changes to the Falcon 9 v.1.1 – to take advantage of the new Merlin 1D engine and changes to the propellant tanks. The original timetable, proposed in 2011, put the rocket’s arrival at SpaceX’s west-coast launch location – Vandenberg Air Force Base in California – at before the end of 2012.

The first launch from Vandenberg was take place in 2013, while the first launch from Cape Canaveral was to take place in late 2013 or 2014. But by mid-2015, delays caused by failures with Falcon 9 test flights caused the first launch to be pushed to late 2016. The rocket has also been relocated to the Kennedy Space Center Launch Complex in Florida.

Artist's concept of the SpaceX Red Dragon spacecraft launching to Mars on SpaceX Falcon Heavy as soon as 2018. Credit: SpaceX — *Artist’s concept of the SpaceX Red Dragon spacecraft launching to Mars on SpaceX Falcon Heavy as soon as 2018. Credit: SpaceX*

SpaceX also announced in July 0f 2016 that it planned to expand its landing facility near Cape Canaveral to take advantage of the reusable technology. With three landing pads now planned (instead of one on land and a drone barge at sea), they hope to be able to recover all of the spent boosters that will be used for the launch of a Falcon Heavy.

Design:

Both the Saturn V and Falcon Heavy were created to do some serious heavy lifting. Little wonder, since both were created for the sole purpose of “slipping the surly bonds” of Earth and putting human beings and cargo onto other celestial bodies. For its part, the Saturn V‘s size and payload surpassed all other previous rockets, reflecting its purpose of sending astronauts to the Moon.

With the Apollo spacecraft on top, it stood 111 meters (363 feet) tall and was 10 meters (33 feet) in diameter, without fins. Fully fueled, the Saturn V weighed 2,950 metric tons (6.5 million pounds), and had a payload capacity estimated at 118,000 kg (261,000 lbs) to LEO, but was designed for the purpose of sending 41,000 kg (90,000 lbs) to Trans Lunar Insertion (TLI).

Later upgrades on the final three missions boosted that capacity to 140,000 kg (310,000 lbs) to LEO and 48,600 kg (107,100 lbs) to the Moon. The Saturn V was principally designed by NASA’s Marshall Space Flight Center in Huntsville, Alabama, while numerous subsystems were developed by subcontractors. This included the engines, which were designed by Rocketdyne, a Los Angeles-based rocket company.

Diagram of Saturn V Launch Vehicle. Credit: NASA/MSFC

The first stage (aka. S-IC) measured 42 m (138 feet) tall and 10 m (33 feet) in diameter, and had a dry weight of 131 metric tons (289,000 lbs) and a total weight of over 2300 metric tons (5.1 million lbs) when fully fueled. It was powered by five Rocketdyne F-1 engines arrayed in a quincunx (four units arranged in a square, and the fifth in the center) which provided it with 34,000 kN (7.6 million pounds-force) of thrust.

The Saturn V consisted of three stages – the S-IC first stage, S-II second stage and the S-IVB third stage – and the instrument unit. The first stage used Rocket Propellant-1 (RP-1), a form of kerosene similar to jet fuel, while the second and third stages relied on liquid hydrogen for fuel. The second and third stage also used solid-propellant rockets to separate during launch.

The Falcon Heavy is based around a core that is a single Falcon 9 with two additional Falcon 9 first stages acting as boosters. While similar in concept to the Delta IV Heavy launcher and proposals for the Atlas V HLV and Russian Angara A5V, the Falcon Heavy was specifically designed to exceed all current designs in terms of operational flexibility and payload. As with other SpaceX rockets, it was also designed to incorporate reusability.

The rocket relies on two stages, with the possibility of more to come, that measure 70 m (229.6 ft) in height and 12.2 m (39.9 ft) in width. The first stage is powered by three Falcon 9 cores, each of which is equipped with nine Merlin 1D engines. These are arranged in a circular fashion with eight around the outside and one in th middle (what SpaceX refers to as the Octaweb) in order to streamline the manufacturing process. Each core also includes four extensible landing legs and grid fins to control descent and conduct landings.

Chart comparing SpaceX's Falcon 9 and Falcon Heavy. Credit: SpaceX — *Chart comparing SpaceX’s Falcon 9 and Falcon Heavy rocket. Credit: SpaceX*

The first stage of the Falcon Heavy relies on Subcooled LOX (liquid oxygen) and chilled RP-1 fuel; while the upper stage also uses them, but under normal conditions. The Falcon Heavy has a total sea-level thrust at liftoff of 22,819 kN (5,130,000 lbf) which rises to 24,681 kN (5,549,000 lbf) as the craft climbs out of the atmosphere. The upper stage is powered by a single Merlin 1D engine which has a thrust of 34 kN (210,000 lbf) and has been modified for use in a vacuum.

Although not a part of the initial Falcon Heavy design, SpaceX has been extending its work with reusable rocket systems to ensure that the boosters and core stage can be recovered. Currently, no work has been announced on making the upper stages recoverable as well, but recent successes recovering the first stages of the Falcon 9 may indicate a possible change down the road.

The consequence of adding reusable technology will mean that the Falcon Heavy will have a reduced payload to GTO. However, it will also mean that it will be able to fly at a much lower cost per launch. With full reusability on all three booster cores, the GTO payload will be approximately 7,000 kg (15,000 lb). If only the two outside cores are reusable while the center is expendable, the GTO payload would be approximately 14,000 kg (31,000 lb).

Cost:

The Saturn V rocket was by no means a small investment. In fact, one of the main reasons for the cancellation of the last three Apollo flights was the sheer cost of producing the rockets and financing the launches. Between 1964 and 1973, a grand total of $6.417 billion USD was appropriated for the sake of research, development, and flights.

Looking at the business end of the Saturn V as it gets moved towards the barge that will transport it to Mississippi. Image: Infinity Science Center. — *A Saturn V rocket viewed from the rear, showing its five Rocketdyne F-1 engines. Credit: Infinity Science Center*

Adjusted to 2016 dollars, that works out to $41.4 billion USD. In terms of individual launches, the Saturn V would cost between $185 and $189 million USD, of which $110 million was spent on production alone. Adjusted for inflation, this works out to approximately $1.23 billion per launch, of which $710 million went towards production.

By contrast, when Musk appeared before the US Senate Committee on Commerce, Science and Transportation in May 2004, he stated that his ultimate goal with the development of SpaceX was to bring the total cost per launch down to $1,100 per kg ($500/pound). As of April 2016, SpaceX has indicated that a Falcon Heavy could lift 2268 kg (8000 lbs) to GTO for a cost of $90 million a launch – which works out to $3968.25 per kg ($1125 per pound).

No estimates are available yet on how a fully-reusable Falcon Heavy will further reduce the cost of individual launches. And again, it will vary depending on whether or not the boosters and the core, or just the external boosters are recoverable. Making the upper stage recoverable as well will lead to a further drop in costs, but will also likely impact performance.

Specifications:

So having covered their backgrounds, designs and overall cost, let’s move on to a side-by-side comparison of these two bad boys. Let’s see how they stack up, pound for pound, when all things are considered – including height, weight, lift payload, and thrust.

	Saturn V:	Falcon Heavy:
Height:	110.6 m (363 ft)	70 m (230 ft)
Diameter:	10.1 m (33 ft)	12.2 m (40 ft)
Weight:	2,970,000 kg (6,540,000 lbs)	1,420,788 kg (3,132,301 lb)
Stages:	3	2+
Engines (1st Stage):	5 Rocketdyne F-1	3 x 9 Merlin 1D
2nd stage	5 Rocketdyne J-2	1 Merlin 1D
3rd stage	1 Rocketdyne J-2
Thrust (1st stage):	34,020 kN	22,918 kN (sea level); 24,681 kN (vacuum)
2nd stage	4,400 kN	934 kN
3rd stage	1,000 kN
Payload (LEO):	140,000 kg (310,000 lbs)	54,400 kg (119,900 lbs)
Payload (TLI):	48,600 kg (107,100 lbs)	16,000 kg (35,000 lbs)

When put next to each other, you can see that the Saturn V has the advantage when it comes to muscle. It’s bigger, heavier, and can deliver a bigger payload to space. On the other hand, the Falcon Heavy is smaller, lighter, and a lot cheaper. Whereas the Saturn V can put a heavier payload into orbit, or send it on to another celestial body, the Falcon Heavy could perform several missions for every one mounted by its competitor.

But whereas the contributions of the venerable Saturn V cannot be denied, the Falcon Heavy has yet to demonstrate its true worth to space exploration. In many ways, its like comparing a retired champion to an up-and-comer who, despite showing lots of promise and getting all the headlines, has yet to win a single bout.

But should the Falcon Heavy prove successful, it will likely be recognized as the natural successor to the Saturn V. Ever since the latter was retired in 1973, NASA has been without a rocket with which to mount long-range crewed missions. And while heavy-lift options have been available – such as the Delta IV Heavy and Atlas V – none have had the performance, payload capacity, or the affordability that the new era of space exploration needs.

In truth, this battle will take several years to unfold. Only after the Falcon Heavy is rigorously tested and SpaceX manages to deliver on their promises of cheaper space launches, a return to the Moon and a mission to Mars (or fail to, for that matter) will we be able to say for sure which rocket was the true champion of human space exploration! But in the meantime, I’m sure there’s plenty of smack talk to be had by fans of both! Preferably in a format that rhymes!

Further Reading: NASA, SpaceX

And a tip of the hat to ERB!

July 21, 2016July 23, 2016 by Matt Williams

Uh, We’re Going To Need A Bigger Landing Pad

The Falcon Heavy, once operational, will be the most powerful rocket in the world. Credit: SpaceX

Since 2000, Elon Musk been moving forward with his vision of a fleet of reusable rockets, ones that will restore domestic launch capability to the US and drastically reduce the cost of space launches. The largest rocket in this fleet is the Falcon Heavy, a variant of the Falcon 9 that uses the same rocket core, with two additional boosters that derived from the Falcon 9 first stage. When it lifts off later this year, it will be the most operational powerful rocket in the world.

More than that, SpaceX intends to make all three components of the rocket fully recoverable. This in turn will mean mean that the company is going to need some additional landing pads to recover them all. As such, the company recently announced that it is seeking federal permission to create second and third landing zones for their incoming rockets on Florida’s Space Coast.

The announcement came on Monday, July 18th, during a press conference at their facility at the Cape Canaveral Air Force Station. As they were quoted as saying by the Orlando Sentinel:

“SpaceX expects to fly Falcon Heavy for the first time later this year. We are also seeking regulatory approval to build two additional landing pads at Cape Canaveral Air Force Station. We hope to recover all three Falcon Heavy rockets, though initially we may attempt drone ship landings [at sea].”

At present, SpaceX relies on both drone ships and their landing site at Cape Canaveral to recover rocket boosters after they return to Earth. Which option they have used depended on how high and how far downrange the rockets traveled. But with this latest announcement, they are seeking to recover all three boosters used in a single Falcon Heavy launch, which could prove to be essential down the road.

Since December, SpaceX has managed to successfully recover five Falcon 9 rockets, both at sea and on land. In fact, the announcement of their intentions to expand their landing facilities on Monday came shortly after a spent Falcon 9 returned to the company’s landing site, shortly after deploying over 2268 kg (5000 lbs) of cargo into space during a nighttime launch.

But the planned launch of the Falcon Heavy – Falcon Heavy Demo Flight 1, which is scheduled to take place this coming December – is expected to break new ground. For one, it will give the private aerospace company the ability to lift over 54 metric tons (119,000 lbs) into orbit, more the twice the payload of a Delta IV Heavy – the highest capacity rocket in service at the moment.

Foremost among these are Elon Musk’s plans to colonize Mars. These efforts will begin in April or May of 2018 with the launch of the Dragon 2 capsule (known as the “Red Dragon”) using a Falcon Heavy. As part of an agreement with NASA to gain more information on Mars landings, the Red Dragon will send a payload to Mars that has yet to be specified.

Beyond that, the details are a bit sketchy; but Musk has indicated that he is committed to mounting a crewed mission to Mars by 2024. And if all goes well with Demo Flight 1, SpaceX expects to follow it up with Falcon Heavy Demo Flight 2 in March of 2017. This launch will see the Falcon Heavy being tested as part of the U.S. Air Force’s Evolved Expendable Launch Vehicle (EELV) certification process.

The rocket will also be carrying some important payloads, such as The Planetary Society’s LightSail 2. This 32 square-meter (344 square-foot) craft, which consists of four ultra-thin Mylar sails, will pick up where its predecessor (the LightSail 1, which was deployed in June 2015) left off – demonstrating the viability of solar sail spacecraft.

Other payloads will include NASA’s Deep Space Atomic Clock and Green Propellant Infusion Mission (GPIM), the US Air Force’s Innovative Space-based radar Antenna Technology (ISAT) satellite, the six Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC-2) satellites, and Georgia Tech’s Prox-1 nanosatellite, which will act as the LightSail 2’s parent sattelite.

Apollo 11's Saturn V rocket prior to the launch July 16, 1969. Screenshot from the 1970 documentary "Moonwalk One." Credit: NASA/Theo Kamecke/YouTube — *Apollo 11’s Saturn V rocket prior to the launch July 16, 1969. Screenshot from the 1970 documentary “Moonwalk One.” Credit: NASA/Theo Kamecke/YouTube*

The Falcon Heavy boasts three Falcon 9 engine cores, each of which is made up of 9 Merlin rocket engines. Together, these engines generate more than 2.27 million kg (5 million pounds) of thrust at liftoff, which is the equivalent of approximately eighteen 747 aircraft. Its lift capacity is also equivalent to the weight of a fully loaded 737 jetliner, complete with passengers, crew, luggage and fuel.

The Saturn V rocket – the workhorse of the Apollo Program, and which made its last flight in 1973 – is only American rocket able to deliver more payload into orbit. This is not surprising, seeing as how the Falcon Heavy was specifically designed for a new era of space exploration, one that will see humans return to the Moon, go to Mars, and eventually explore the outer Solar System.

Fingers crossed that everything works out and the Falcon Heavy proves equal to the enterprise. The year of 2024 is coming fast and many of us are eager to see boots being put to red soil! And be sure to enjoy this animation of the Falcon Heavy in flight:

Further Reading: Orlando Sentinel

July 21, 2016July 21, 2016 by Bob King

Viking: Remembering Humanity’s First Successful Mission On Mars Surface

Taken by the Viking 1 lander shortly after it touched down on Mars, this image is the first photograph ever taken from the surface of Mars. It was taken on July 20, 1976. The primary objectives of the Viking mission, which was composed of two spacecraft, were to obtain high-resolution images of the Martian surface, characterize the structure and composition of the atmosphere and surface and search for evidence of life on Mars. Credit: NASA

July 20. Sound like a familiar date? If you guessed that’s when we first set foot on the Moon 47 years ago, way to go! But it’s also the 40th anniversary of Viking 1 lander, the first American probe to successfully land on Mars.

The Russians got there first on December 2, 1971 when their Mars 3 probe touched down in the Mare Sirenum region. But transmissions stopped just 14.5 seconds later, only enough time for the crippled lander to send a partial and garbled photo that unfortunately showed no identifiable features.

The late, great Carl Sagan stands next to a model of the Viking lander. Credit: NASA

Viking 1 touched down on July 20, 1976 in Chryse Planitia, a smooth, circular plain in Mars’ northern equatorial region and operated for six years, far beyond the original 90 day mission. Its twin, Viking 2, landed about 4,000 miles (6,400 km) away in the vast northern plain called Utopia Planitia several weeks later on September 3. Both were packaged inside orbiters that took pictures of the landing sites before dispatching the probes.

The first color photo taken of the Martian surface by the Viking 1 lander on July 21, 1976. The rock strewn landscape is a familiar one seen in photos taken by many landers since. Credit: NASA

Viking 1 was originally slated to land on July 4th to commemorate the 200th year of the founding of the United States. Some of you may remember the bicentennial celebrations underway at the time. Earlier photos taken by Mariner 9 helped mission controllers pick what they thought was a safe landing site, but when the Viking 1 orbiter arrived and took a closer look, NASA deemed it too bouldery for a safe landing, so they delayed the the probe’s arrival until a safer site could be chosen. Hence the July 20th touchdown date.

My recollection at the time was that that particular date was picked to coincide with the first lunar landing.

I’ll never forget the first photo transmitted from the surface. I had started working at the News Gazette in Champaign, Ill. earlier that year in the photo department. On July 20 I joined the wire editor, a kindly. older gent named Raleigh, at the AP Photofax machine and watched the black and white image creep line-by-line from the machine. Still damp with ink, I lifted the sodden sheet into my hands, totally absorbed. Two things stood out: how incredibly sharp the picture was and ALL THOSE ROCKS! Mars looked so different from the Moon.

The Viking 1 Lander sampling arm created a number of deep trenches as part of the surface composition and biology experiments on Mars. The digging tool on the sampling arm (at lower center) could scoop up samples of material and deposit them into the appropriate experiment. Some holes were dug deeper to study soil which was not affected by solar radiation and weathering. The trenches in this ESE looking image are in the "Sandy Flats" area of the landing site at Chryse Planitia. Credit: NASA — The Viking 1 Lander sampling arm created a number of deep trenches as part of the surface composition and biology experiments on Mars. The digging tool on the sampling arm (at lower center) could scoop up samples of material and deposit them into the appropriate experiment. Some holes were dug deeper to study soil which was not affected by solar radiation and weathering. Credit: NASA

One day later, Viking 1 returned the first color photo from the surface and continued to operate, taking photos and doing science for 2,307 days until November 11, 1982, a record not broken until May 2010 by NASA’s Opportunity rover. It would have continued humming along for who knows how much longer were it not for a faulty command sent by mission control that resulted in a permanent loss of contact.

The first Mars panorama taken in Chryse Plantia by Viking 1. Credit: NASA — The first Mars panorama taken in Chryse Plantia by Viking 1. Click to supersize. Credit: NASA

Viking 2 soldiered on until its batteries failed on April 11, 1980. Both landers characterized the Martian weather and radiation environment, scooped up soil samples and measured their elemental composition and send back lots of photos including the first Martian panoramas.

Each lander carried three instruments designed to look for chemical or biological signs of living or once-living organisms. Soil samples scooped up by the landers’ sample arms were delivered to three experiments in hopes of detecting organic compounds and gases either consumed or released by potential microbes when they were treated with nutrient solutions. The results from both landers were similar: neither suite of experiments found any organic (carbon-containing) compounds nor any definitive signs of Mars bugs.

The first color picture taken by Viking 2 on the Martian surface shows a rocky reddish surface much like that seen by Viking 1 more than 4000 miles away. Credit: NASA — The first color picture taken by Viking 2 on the Martian surface shows a rocky reddish surface much like that seen by Viking 1 more than 4,000 miles away. Credit: NASA

Not that there wasn’t some excitement. The Labeled Release experiment (LC) actually did give positive results. A nutrient solution was added to a sample of Martian soil. If it contained microbes, they would take in the nutrients and release gases. Great gobs of gas were quickly released! As if the putative Martian microbes only needed a jigger of NASA’s chicken soup to find their strength. But the complete absence of organics in the soil made scientists doubtful that life was the cause. Instead it was thought that some inorganic chemical reaction must be behind the release. Negative results from the other two experiments reinforced their pessimism.

Frost on Utopia Planitia photographed by Viking 2. Credit NASA — Frost on Utopia Planitia photographed by Viking 2. Click to visit NASA’s Viking image archive (not to miss!) Credit NASA

Fast forward to 2008 when the Phoenix lander detected strongly oxidizing perchlorates originating from the interaction of strong ultraviolet light from the Sun with soils on the planet’s surface. Since Mars lacks an ozone layer, perchlorates may not only be common but also responsible for destroying much of Mars’ erstwhile organic bounty. Other scientists have reexamined the Viking LC data in recent years and concluded just the opposite, that the gas release points to life.

A fun, “period” movie about the Viking Mission to Mars

Seems to me it’s high time we should send a new suite of experiments designed to find life. Then again, maybe we won’t have to. The Mars 202o Mission will cache Martian rocks for later pickup, so we can bring pieces of Mars back to Earth and perform experiments to our heart’s content.

July 20, 2016November 27, 2016 by Matt Williams

How Fast Does Venus Rotate?

The planet Venus, as imaged by the Magellan 10 mission. Credit: NASA/JPL — The planet Venus, as imaged by the Magellan 10 mission. The planet's inhospitable surface makes exploration extremely difficult. Credit: NASA/JPL

Venus is often refereed to as “Earth’s sister planet”, thanks to the number of things it has in common with our planet. As a terrestrial planet, it is similarly composed of silicate rock and metals – which are differentiated between a metal core and a silicate crust and mantle. It also orbits within our Sun’s habitable zone, and had a similarly violent volcanic past.

But of course, there are also some major differences between our two planets. For one, Venus has an atmosphere that is incredibly dense (92 times that of Earth, in fact) and reaches temperatures that are hot enough to melt lead. In addition, the planet’s rotation is immensely slow by comparison, taking 243.025 days to complete a single rotation, and rotating backwards relative to Earth.

When discussing Venus’ rotation, it is important to note certain distinctions. Rotation is the time it takes for a planet to spin once on its axis. This is different from a planet’s revolution, which is the time it takes for a planet to orbit around another object (i.e. the Sun). So while it takes the Earth one day (24 hours) to rotate once on its axis, it takes one year (365.256 days) to revolve once around the Sun.

Earth and Venus' orbit compared. Credit: Sky and Telescope — *Earth and Venus’ orbit compared. Credit: Sky and Telescope*

Orbital Period:

In Venus’ case, things work a little differently. For starters, it 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.

The planet completes a revolution around the Sun every 224.65 Earth days, which means that a year on Venus last about 61.5% as long as a year on Earth. Evey 584 days, Venus completes an interior conjunction, where it lies between Earth and the Sun. It is at this point that Venus makes the closest approach to Earth of any planet, at an average distance of 41 million km.

Rotational Period:

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 243.025 Earth days to complete a single rotation. This is not only the slowest rotation period of any planet, it also means that a single day on Venus lasts longer than a Venusian year.

Phases of Venus during 2004 photographed through a telescope. When very close to inferior conjunction (bottom right) the crescent is seen to extend fully around the planet. Credit: Statis Kalyva / Wikipedia

And, as noted earlier, Venus’ rotation is backwards, relative to Earth and the other bodies in the Solar System. Technically, this means that its rotational period is -243,025 days. It also means that if you could view the Solar System from the position above its celestial north pole, all of the planets (except for Uranus, which rotates on its side!) would appear to be rotating clockwise.

Venus, however, would appear to be rotating in a clockwise direction. Because of this, if you could stand on the surface of Venus, you would witness the Sun rising in the west and setting in the east. But you would be waiting a very long time to see this happen! Read on to find out why…

Sidereal vs. Solar Day:.

Another important thing to consider is the difference between a sidereal day and a solar day. A sidereal day corresponds to the amount of time it takes for a planet to rotate once on its axis, which in Venus’ case takes 243.025 Earth days. A solar day, by contrast, refers to the amount of time it takes for the Sun to reappear at the same point in the sky (i.e. between one sunrise/sunset and the next).

A Venusian (aka. Cytherean) Solar Day is the equivalent to 116.75 days on Earth, which means that it takes almost 117 days for the sun to rise, set, and return to the same place in the sky. Doing the math, we then see that a single year on Venus (224.65 Earth days) works out to just 1.92 Venusian (solar) days. Not exactly the basis for a good calendar system, is it?

Another view from the Solar Dynamics Observatory as Venus moves across the face of the Sun. Credit: NASA/SDO — *View of Venus from the Solar Dynamics Observatory. If viewed from the surface of Venus, the Sun would be moving from west to east in the sky. Credit: NASA/SDO*

Yes, when it comes to the planet Venus, things work quite differently than they do here on Earth. Not only does a day last over half a year on our “Sister Planet”, but the Sun rises and sets on the opposite horizons, and travels across the sky in the opposite direction. The reason for this, according to astronomers, is that billions of years ago (early in the planet’s history) Venus was impacted by another large planet.

The combined momentum between the two objects averaged out to the current rotational speed and direction, causing Venus to spin very slowly in its current retrograde motion. Someday, if human beings colonize there (perhaps in floating cities) they will have to learn to get used to a day that lasts over 2800 Earth hours, not to mention sunrises and sunsets happening on the wrong horizon!

We have written many interesting articles about Venus here at Universe Today. Here’s Interesting Facts About Venus, How Long is a Day on Venus?, How Long is a Year on Venus?, What is the Average Surface Temperature on Venus?, New Map Hints at Venus’ Wet, Volcanic Past and Venus Compared to Earth.

Want more information on Venus? Here’s a link to Hubblesite’s News Releases about Venus, and here’s a link to NASA’s Solar System Exploration Guide on Venus.

We have recorded a whole episode of Astronomy Cast that’s only about planet Venus. Listen to it here, Episode 50: Venus.

July 19, 2016July 23, 2016 by David Dickinson

See All Five Naked Eye Planets in the Dusk Sky at Once

Solar System — An Iphone solar system family portrait. Image credit and copyright: Andrew Symes (@Failedprotostar)

Hosting an evening star party this summer? You’re in for a treat. Starting later this week, all five naked eye planets (Mercury, Venus, Mars, Jupiter and Saturn) are visible in the evening sky at dusk for a brief few weeks. We had a similar lineup in the dawn sky earlier in 2016, as the Earth had all the inner planets in its forward-facing view — now, we see these same planets in our collective rear view mirror, as we lap Mars, Jupiter and Saturn on the inner track, while Mercury and Venus race to catch up with us.

Dusk on the evening of August 8th. Image credit: Stellarium. — Dusk on the evening of August 8th, looking to the southwest. Image credit: Stellarium.

At their narrowest, the planets from Saturn to Mercury fit within a span just 75 degrees wide in the last half of August. A wide field all-sky shot should catch ’em all in the same frame at once. This isn’t a ‘grand conjunction’ in a strict sense. To have all five planets visible, you need the slowest and outermost of the five — Jupiter and Saturn, with orbital periods of 11.9 and 29.5 years respectively — in the same general swath of sky. Both are headed towards conjunction on December 21^st, 2020, making such groupings more frequent as they race past the other three. The next true quintuple grand conjunction occurs on September 8^th, 2040, when all 5 planets span just 9.3 degrees of the sky… the closest span since September 18^th, 1186!

Can you see 'em? Five planets from Monte Mario in Rome on February 2nd, 2016. Image credit: Gianluca Masi/The Virtual Telescope project. — Can you see ’em? Five planets from Monte Mario in Rome on February 2nd, 2016. Image credit: Gianluca Masi/The Virtual Telescope project.

There’s a lot to watch out for in the next few weeks. Here’s a who’s who of planets this July and August, from east to west:

Saturn: shining at magnitude +0.4 in the constellation Ophiuchus, Saturn is fresh off of opposition on June 3rd. Riding high in the southeast at dawn, Saturn makes a close 4.4 degree pass near Mars on August 24^th, and the pair makes a straight line completed by the bright star Antares on the same date.

Mars: High to the south in the constellation Libra at dusk, Mars begins its slow dive into the dusk during the last half of 2016. Currently shining at a respectable magnitude -0.9, Mars passed opposition on May 22nd and is headed towards a grand opposition in 2018, nearly as close as the historic close pass of 2003.

Jupiter: Sitting in the constellation Leo, Jupiter shines at magnitude -1.6 and is about 20-30 degrees above the southwestern horizon at dusk. Jupiter passed quadrature 90 degrees east of the Sun on June 4^th and opposition for 2016 on March 8th.

Venus: The bashful planet of the group, Venus is slowly appearing from behind the Sun low in the dusk and headed for a brilliant dusk apparition later in 2016 and early 2017. Currently 3 degrees east of the Sun on July 31^st, Venus reaches greatest elongation 47 degrees east of the Sun on January 12^th, 2017. We’ve just been able to begin spying Venus using binocs last week from the rooftop of our Casablanca Air BnB. Follow that planet, as Venus makes a close 6′ pass near Jupiter on August 27th.

Mercury: And the innermost planet makes five, as Mercury reaches greatest elongation 27 degrees east of the Sun on August 16th. When can you first catch sight of Mercury, completing the fivesome? Jupiter and Venus actually make great bookends in the hunt, as +0.5 magnitude Mercury wanders between them through early August. It’s too bad dusk twilight obscured the view this past weekend, as both Mercury and Venus photobombed the Beehive Cluster M44 in Cancer. Mercury also passes 20′ from the bright star Regulus on July 30^th.

Looking west on the evening of July 19th, 2016. Credit Starry Night Education Software.

But wait, there’s more. The Moon passes New on August 2nd, entering back into the dusk sky. The one day old Moon will pass the grouping of Venus, Regulus and Mercury on the evening of August 4^th, actually occulting (passing in front of) Mercury for the southernmost tip of South America. The Moon then moves on to occult Jupiter for good measure on August 6^th for the South Pacific and southeast Asia in the daytime. Finally, the waxing gibbous Moon makes a wide pass near Mars, Antares and Saturn on the evening of August 12^th, on the same evening that the 2016 Perseids are due to occur.

The footprint of the August 4th occultation of Mercury by the Moon. Image credit: Occult 4.2 software.

The Moon also reaches the nearest apogee (think ‘closest far point’) of the year, at 404,265 kilometers from the Earth on August 10th and reaches Full on August 18^th, featuring a subtle penumbral eclipse and the start of eclipse season 2 of 2 for 2016.

More on all of these events in the coming weeks. So, if you find yourself out hunting Pokémon G0 creatures ’til the late dusk hours this summer, don’t forget to look up at the greatest show in the solar system!

July 18, 2016September 20, 2016 by Matt Williams

ROCKY Exercise Device Will Help Keep Deep Space A Fit Place

NASA has unveiled a new exercise device that will be used by Orion crews to stay healthy on their mission to Mars. Credit: NASA

Going into space comes with its share of risks. In addition to the possibility of a catastrophic failure happening during take-off or landing, and having your craft pinholed by a micrometeorite, there are also the dangers of spending extended periods in space. Beyond that, there are also the slow, degenerative effects that spending an extended amount of time in a weightless environment can have on your body.

While astronauts on the ISS have enough space for the work-out equipment they need to help reduce these effects (i.e. muscle degeneration and loss of bone density), long-range missions are another matter. Luckily, NASA has plans for how astronauts can stay healthy during their upcoming “Journey to Mars“. It’s known as the Resistive Overload Combined with Kinetic Yo-Yo (ROCKY) device, which will be used aboard the Orion spacecraft.

For years, engineers at NASA and in the private sector have been working to create the components that will take astronauts to the Red Planet in the 2030s. These include the Space Launch System (SLS) and the Orion Multi Purpose Crew Capsule. At the same time, scientists and engineers at the Ohio-based Zin Technologies company – with the support of the NASA Human Research Program’s Exploration Exercise Equipment project – were busy developing the equipment needed to keep the Martian crews healthy and fit in space.

In this cutaway of the Orion crew module, the ROCKY exercise device in blue sits below the side hatch astronauts will use to get in and out of the spacecraft. Credit: NASA — *Cutaway of the Orion crew module, showing the ROCKY exercise device in blue, below the side hatch that astronauts will use to get in and out of the spacecraft. Credit: NASA*

One of the biggest challenges was making a device that is robust enough to provide a solid work-out, but still be compact and light-weight enough to fit inside the space capsule. What they came up with was ROCKY, a rowing machine-like tool that can accommodate both aerobic activity and strength training. Using loads that simulate up to 180 kg (400 pounds) of resistance, astronauts will be able to perform excises like squats, deadlifts and heel raises, as well as upper body exercises like bicep curls and upright rows.

In the past, astronauts aboard the ISS have relied on equipment like the Mini Exercise Device-2 or the Treadmill Vibration Isolation System (TVIS) to reduce the risks of bone-density loss and muscle degeneration. But as Gail Perusek – the deputy project manager for NASA’s Exploration Exercise Equipment project – explained, developing exercise equipment for the Journey to Mars required something new:

“ROCKY is an ultra-compact, lightweight exercise device that meets the exercise and medical requirements that we have for Orion missions. The International Space Station’s exercise devices are effective but are too big for Orion, so we had to find a way to make exercising in Orion feasible.”

The device can also be customized, and incorporates the best features from a second device known as the Device for Aerobic and Resistive Training (DART). These include a servo-motor programmed to deliver a load profile that feels very similar to free weights. The DART was developed by TDA Research, a Denver-based R&D company, with the support of NASA’s Small Business Innovation Research Program. It was evaluated alongside the ROCKY during the equipment selection process.

*The ROCKY device in action. Credit: NASA*

In addition to being used for the crewed mission to Mars, the ROCKY device is likely to become a permanent feature aboard the Orion capsule, which will make it a mainstay for all of NASA’s proposed long-duration missions.

As Cindy Haven, the project manager for the Exploration Exercise Equipment Project, explained: “Our long-term goal is to develop a device that’s going to work for us for exploration. Between now and the mission, we’ll have different phases where we’re going to evaluate it for functionality, usability and durability to refine its design.”

The ROCKY device will be tested for the first time on Exploration Mission-2 (EM-2), the first mission where the spacecraft will be launched with a crew aboard. Th ROCKY will be located near the side hatch of the spacecraft, which astronauts will use to get in and out of the capsule. After the Orion is launched, the crew’s seats will be collapsed to provide more interior space for the astronauts as they work out.

And while the early missions using the Orion capsule will span only a few weeks at a time, staying fit will be important in the unlikely event that the astronauts need to get out of the crew module unassisted after splashdown. In the meantime, NASA will be spending the next few years refining the device to optimize it not only for near-term crewed Orion missions, but for potential uses on future long-duration missions.

These will include the all-important launch where the Orion will dock with a habitat in the area of space around the moon. These missions are part of Phase II of NASA’s Mars mission, which is known as the “Proving Ground” phase. Scheduled to begin in 2030, this phase will involve the last elements of the mission being launched to cis-lunar orbit, and then all the equipment being sent to near-Mars space for pre-deployment.

The development team that will oversee future refinements will include engineers and scientists from Glenn Research Center in Cleveland, Ohio, and Johnson Space Center in Houston. In addition to building the hardware and ensuring that it is certified for flight, they will also be responsible for incorporating lessons learned from the development of equipment built for the ISS.

If all goes well in the coming years, the team even plans to include ROCKY into the International Space Station’s already impressive array of workout machines. Just another way for the astronauts to beat the slow, degenerative effects of floating freely in space!

Further Reading: NASA