Venus Archives

February 20, 2015December 23, 2015 by Elizabeth Howell

Interesting Facts About Venus

False color radar topographical map of Venus provided by Magellan. Credit: Magellan Team/JPL/NASA

Venus was once considered a twin to Earth, as it’s roughly the same size and is relatively close to our planet. But once astronomers looked at it seriously in the past half-century or so, a lot of contrasts emerged. The biggest one — Venus is actually a hothouse planet with a runaway greenhouse effect, making it inhospitable to life as we know it. Here are some more interesting facts about Venus.

1. Venus’ atmosphere killed spacecraft dead very quickly:
You sure don’t want to hang around on Venus’ surface. The pressure there is so great that spacecraft need shielding to survive. The atmosphere is made up of carbon dioxide with bits of sulfuric acid, NASA says, which is deadly to humans. And if that’s not bad enough, the temperature at the surface is higher than 470 degrees Celsius (880 degrees Fahrenheit). The Soviet Venera probes that ventured to the surface decades ago didn’t last more than two hours.

2. But conditions are more temperate higher in the atmosphere:
While you still couldn’t breathe the atmosphere high above Venus’ surface, at about 50 kilometers (31 miles) you’ll at least find the same pressure and atmosphere density as that of Earth. A very preliminary NASA study suggests that at some point, we could deploy airships for humans to explore Venus. And the backers suggest it may be more efficient to go to Venus than to Mars, with one large reason being that Venus is closer to Earth.

Artist's conception of the High Altitude Venus Operational Concept (HAVOC) mission, a far-out concept being developed by NASA, approaching the planet. Credit: NASA Langley Research Center/YouTube (screenshot) — Artist’s conception of the High Altitude Venus Operational Concept (HAVOC) mission, a far-out concept being developed by NASA, approaching the planet. Credit: NASA Langley Research Center/YouTube (screenshot)

3. Venus is so bright it is sometimes mistaken for a UFO:
The planet is completely socked in by cloud, which makes it extremely reflective to observers looking at the sky on Earth. Its brightness is between -3.8 and -4.8 magnitude, which makes it brighter than the stars in the sky. In fact, it’s so bright that you can see it go through phases in a telescope — and it can cast shadows! So that remarkable appearance can confuse people not familiar with Venus in the sky, leading to reports of airplanes or UFOs.

4. And those clouds mean you can’t see the surface:
If you were to look at Venus with your eyes, you wouldn’t be able to see its surface. That’s because the clouds are so thick that they obscure what is below. NASA got around that problem when it sent the Magellan probe to Venus for exploration in the 1990s. The probe orbited the planet and got a complete surface picture using radar.

Artist's impression of the surface of Venus Credit: ESA/AOES — *Artist’s impression of the surface of Venus Credit: ESA/AOES*

5. Venus has volcanoes and a fresh face:
Venus has fresh lava flows on its surface, which implies that volcanoes erupted anywhere from the past few hundred years to the past three million years. What this means is there are few impact craters on the surface, likely because the lava flowed over them and filled them in. While scientists believe the volcanoes are responsible, the larger question is how frequently this occurs.

6. Venus has a bizarre rotation:
Venus not only rotates backwards compared to the other planets, but it rotates very slowly. In fact, a day on Venus (243 days) lasts longer than it takes the planet to orbit around the Sun (225 days). Even more strangely, the rotation appears to be slowing down; Venus is turning 6.5 minutes more slowly in 2014 than in the early 1990s. One theory for the change could be the planet’s weather; its thick atmosphere may grind against the surface and slow down the rotation.

Artist's conception of Venus Express doing an aerobraking maneuver in the atmosphere in 2014. Credit: ESA–C. Carreau — *Artist’s conception of Venus Express doing an aerobraking maneuver in the atmosphere in 2014. Credit: ESA–C. Carreau*

7. Venus has no moons or rings:
The two planets closest to the Sun have no rings or moons, which puts Venus in the company of only one other world: Mercury. Every other planet in the Solar System has one or the other, or in many cases both! Why this is is a mystery to scientists, but they are doing as much comparison of different planets as possible to understand what’s going on.

8. Venus appears to be a spot where spacecraft go to extremes:
We briefly mentioned the Venera probes that landed on the surface, but that’s not the only unusual spacecraft activity at Venus. In 2014, the European Space Agency put an orbiter — that’s right, a spacecraft not designed to survive the atmosphere — into the upper parts of Venus’ dense atmosphere. Venus Express did indeed survive the encounter (before it ran out of gas), with the goal of providing more information about how the atmosphere looks at high altitudes. This could help with landings in the future.

As you can see, Venus is an interesting, mysterious, and extremely hostile world. With such a corrosive atmosphere, such incredible heat, a volcanically-scarred surface, and thick clouds of toxic gas, one would have to be crazy to want to live there. And yet, there are some who believe Venus could be terraformed for human use, or at the very least explored using airships, in the coming generations.

But that’s the thing about interesting places. Initially, they draw their fair share of research and attention. But eventually, the dreamers and adventurers come.

February 19, 2015December 23, 2015 by Ken Kremer

25 Years Since Voyager’s ‘Pale Blue Dot’ Images

These six narrow-angle color images were made from the first ever "portrait" of the solar system taken by Voyager 1 on Valentine’s Day on Feb. 14, 1990, which was more than 4 billion miles from Earth and about 32 degrees above the ecliptic. Venus, Earth, Jupiter, and Saturn, Uranus, Neptune are seen in these blown-up images, from left to right and top to bottom. Credit: NASA/JPL-Caltech

A quarter of a century has passed since NASA’s Voyager 1 spacecraft snapped the iconic image of Earth known as the “Pale Blue Dot” that shows all of humanity as merely a tiny point of light.

The outward bound Voyager 1 space probe took the ‘pale blue dot’ image of Earth 25 years ago on Valentine’s Day, on Feb. 14, 1990 when it looked back from its unique perch beyond the orbit of Neptune to capture the first ever “portrait” of the solar system from its outer realms.

Voyager 1 was 4 billion miles from Earth, 40 astronomical units (AU) from the sun and about 32 degrees above the ecliptic at that moment.

The idea for the images came from the world famous astronomer Carl Sagan, who was a member of the Voyager imaging team at the time.

He head the idea of pointing the spacecraft back toward its home for a last look as a way to inspire humanity. And to do so before the imaging system was shut down permanently thereafter to repurpose the computer controlling it, save on energy consumption and extend the probes lifetime, because it was so far away from any celestial objects.

Sagan later published a well known and regarded book in 1994 titled “Pale Blue Dot,” that refers to the image of Earth in Voyagers series.

This narrow-angle color image of the Earth, dubbed "Pale Blue Dot," is a part of the first ever "portrait" of the solar system taken by Voyager 1 on Valentine’s Day on Feb. 14, 1990. Credit: NASA/JPL-Caltech — This narrow-angle color image of the Earth, dubbed “Pale Blue Dot,” is a part of the first ever “portrait” of the solar system taken by Voyager 1 on Valentine’s Day on Feb. 14, 1990. Credit: NASA/JPL-Caltech

“Twenty-five years ago, Voyager 1 looked back toward Earth and saw a ‘pale blue dot,’ ” an image that continues to inspire wonderment about the spot we call home,” said Ed Stone, project scientist for the Voyager mission, based at the California Institute of Technology, Pasadena, in a statement.

Six of the Solar System’s nine known planets at the time were imaged, including Venus, Earth, Jupiter, and Saturn, Uranus, Neptune. The other three didn’t make it in. Mercury was too close to the sun, Mars had too little sunlight and little Pluto was too dim.

Voyager snapped a series of images with its wide angle and narrow angle cameras. Altogether 60 images from the wide angle camera were compiled into the first “solar system mosaic.”

Voyager 1 was launched in 1977 from Cape Canaveral Air Force Station in Florida as part of a twin probe series with Voyager 2. They successfully conducted up close flyby observations of the gas giant outer planets including Jupiter, Saturn, Uranus and Neptune in the 1970s and 1980s.

Both probes still operate today as part of the Voyager Interstellar Mission.

“After taking these images in 1990, we began our interstellar mission. We had no idea how long the spacecraft would last,” Stone said.

Hurtling along at a distance of 130 astronomical units from the sun, Voyager 1 is the farthest human-made object from Earth.

Solar System Portrait - 60 Frame Mosaic. The cameras of Voyager 1 on Feb. 14, 1990, pointed back toward the sun and took a series of pictures of the sun and the planets, making the first ever "portrait" of our solar system as seen from the outside. Missing are Mercury, Mars and Pluto Credit: NASA/JPL-Caltech — Solar System Portrait – 60 Frame Mosaic. The cameras of Voyager 1 on Feb. 14, 1990, pointed back toward the sun and took a series of pictures of the sun and the planets, making the first ever “portrait” of our solar system as seen from the outside. Missing are Mercury, Mars and Pluto. Credit: NASA/JPL-Caltech

Voyager 1 still operates today as the first human made instrument to reach interstellar space and continues to forge new frontiers outwards to the unexplored cosmos where no human or robotic emissary as gone before.

Here’s what Sagan wrote in his “Pale Blue Dot” book:

“That’s here. That’s home. That’s us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives. … There is perhaps no better demonstration of the folly of human conceits than this distant image of our tiny world.”

Stay tuned here for Ken’s continuing Earth and planetary science and human spaceflight news.

Ken Kremer

February 16, 2015December 23, 2015 by Elizabeth Howell

Interesting Facts About The Planets

A montage of planets and other objects in the solar system. Credit: NASA/JPL

While the universe is a big place to study, we shouldn’t forget our own backyard. With eight planets and a wealth of smaller worlds to look at, there’s more than enough to learn for a few lifetimes!

So what are some of the most surprising things about the planets? We’ve highlighted a few things below.

1. Mercury is hot, but not too hot for ice

The closest planet to the Sun does indeed have ice on its surface. That sounds surprising at first glance, but the ice is found in permanently shadowed craters — those that never receive any sunlight. It is thought that perhaps comets delivered this ice to Mercury in the first place. In fact, NASA’s MESSENGER spacecraft not only found ice at the north pole, but it also found organics, which are the building blocks for life. Mercury is way too hot and airless for life as we know it, but it shows how these elements are distributed across the Solar System.

2. Venus doesn’t have any moons, and we aren’t sure why.

Both Mercury and Venus have no moons, which can be considered a surprise given there are dozens of other ones around the Solar System. Saturn has over 60, for example. And some moons are little more than captured asteroids, which may have been what happened with Mars’ two moons, for example. So what makes these planets different? No one is really sure why Venus doesn’t, but there is at least one stream of research that suggests it could have had one in the past.

3. Mars had a thicker atmosphere in the past.

What a bunch of contrasts in the inner Solar System: practically atmosphere-less Mercury, a runaway hothouse greenhouse effect happening in Venus’ thick atmosphere, temperate conditions on much of Earth and then a thin atmosphere on Mars. But look at the planet and you can see gullies carved in the past from probable water. Water requires more atmosphere, so Mars had more in the past. Where did it go? Some scientists believe it’s because the Sun’s energy pushed the lighter molecules out of Mars’ atmosphere over millions of years, decreasing the thickness over time.

4. Jupiter is a great comet catcher.

The most massive planet in the Solar System probably had a huge influence on its history. At 318 times the mass of Earth, you can imagine that any passing asteroid or comet going near Jupiter has a big chance of being caught or diverted. Maybe Jupiter was partly to blame for the great bombardment of small bodies that peppered our young Solar System early in its history, causing scars you can still see on the Moon today. And in 1994, astronomers worldwide were treated to a rare sight: a comet, Shoemaker-Levy 9, breaking up under Jupiter’s gravity and slamming into the atmosphere.

Fragmentation of comets is common. Many sungrazers are broken up by thermal and tidal stresses during their perihelions. At top, an image of the comet Shoemaker-Levy 9 (May 1994) after a close approach with Jupiter which tore the comet into numerous fragments. An image taken by Andrew Catsaitis of components B and C of Comet 73P/Schwassmann–Wachmann 3 as seen together on 31 May 2006 (Credit: NASA/HST, Wikipedia, A.Catsaitis)

5. No one knows how old Saturn’s rings are

There’s a field of ice and rock debris circling Saturn that from afar, appear as rings. Early telescope observations of the planet in the 1600s caused some confusion: does that planet have ears, or moons, or what? With better resolution, however, it soon became clear that there was a chain of small bodies encircling the gas giant. It’s possible that a single moon tore apart under Saturn’s strong gravity and produced the rings. Or, maybe they’ve been around (pun intended) for the last few billion years, unable to coalesce into a larger body but resistant enough to gravity not to break up.

6. Uranus is more stormy than we thought.

When Voyager 2 flew by the planet in the 1980s, scientists saw a mostly featureless blue ball and some assumed there wasn’t much activity going on on Uranus. We’ve had a better look at the data since then that does show some interesting movement in the southern hemisphere. Additionally, the planet drew closer to the Sun in 2007, and in more recent years telescope probing has shown some storms going on. What is causing all this activity is difficult to say unless we were to send another probe that way. And unfortunately, there are no missions yet that are slated for sure to zoom out to that part of the Solar System.

Infrared images of Uranus showing storms at 1.6 and 2.2 microns obtained Aug. 6, 2014 by the 10-meter Keck telescope. Credit: Imke de Pater (UC Berkeley) & Keck Observatory images.

7. Neptune has supersonic winds.

While on Earth we are concerned about hurricanes, the strength of these storms is nowhere near what you would find on Neptune. At its highest altitudes, according to NASA, winds blow at more than 1,100 miles per hour (1,770 kilometers per hour). To put that in context, that’s faster than the speed of sound on Earth, at sea level. Why Neptune is so blustery is a mystery, especially considering the Sun’s heat is so little at its distance.

8. You can see Earth’s magnetic field at work during light shows.

We have a magnetic field surrounding our planet that protects us from the blasts of radiation and particles the Sun sends our way. Good thing, too, because such flare-ups could prove deadly to unprotected people; that’s why NASA keeps an eye on solar activity for astronauts on the International Space Station, for example. At any rate, when you see auroras shining in the sky, that’s what happens when the particles from the Sun flow along the magnetic field lines and interact with Earth’s upper atmosphere.

Universe Today has many articles on interesting facts about the planets. Start with 10 facts about Mercury and 10 facts about Venus. You may also want to check out the 10 facts about Mars. Astronomy Cast also has a number of podcasts about the planets, including one on Earth.

January 21, 2015December 23, 2015 by Nancy Atkinson

A Swirling Vortex at Venus’ South Pole

A mass of swirling gas and cloud at Venus’ south pole. Credit: ESA/VIRTIS/INAF-IASF/Obs. de Paris-LESIA/Univ. Oxford.

Here’s the latest view of the mass of swirling gas and clouds at Venus’ south pole. The Venus Express’s Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) has been keeping an eye on this polar vortex since the spacecraft arrived and discovered this huge storm in 2006. During the mission, VIRTIS has seen the vortex constantly transform, morphing from a double vortex into a squashed shape and into the eye-like structure seen here.

This image was taken in April 2007 but was just released this week.

Venus has a very choppy and fast-moving atmosphere, even though wind speeds are much slower at the planet’s surface. At the cloud tops about 70 km above the surface, winds can reach 400 km/h. At this altitude, Venus’ atmosphere spins about 60 times faster than the planet itself. Compared to Earth, this is a dizzying speed: even Earth’s fastest winds move at most about 30% of our planet’s rotation speed.

These polar vortices form when heated air from equatorial latitudes rises and spirals towards the poles, carried by the fast winds. As the air converges on the pole and then sinks.

High velocity winds spin westwards around the planet, and take just four days to complete a rotation. This ‘super-rotation’, combined with the natural recycling of hot air in the atmosphere, would induce the formation of a vortex structure over each pole.

A video of the vortex, made from 10 images taken over a period of five hours, can be seen here. The vortex rotates with a period of around 44 hours.

Source: ESA

January 16, 2015December 23, 2015 by Matt Williams

Some of the Best Pictures of the Planets in our Solar System

The Eight Planets of our Solar System. Credit: IAU

Our Solar System is a pretty picturesque place. Between the Sun, the Moon, and the Inner and Outer Solar System, there is no shortage of wondrous things to behold. But arguably, it is the eight planets that make up our Solar System that are the most interesting and photogenic. With their spherical discs, surface patterns and curious geological formations, Earth’s neighbors have been a subject of immense fascination for astronomers and scientists for millennia.

And in the age of modern astronomy, which goes beyond terrestrial telescopes to space telescopes, orbiters and satellites, there is no shortage of pictures of the planets. But here are a few of the better ones, taken with high-resolutions cameras on board spacecraft that managed to capture their intricate, picturesque, and rugged beauty.

Mercury, as imaged by the MESSENGER spacecraft, revealing parts of the never seen by human eyes. Image Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington — *Mercury, as imaged by the MESSENGER spacecraft, revealing parts never before seen by human eyes. Image Credit: NASA/Johns Hopkins University/Carnegie Institution of Washington*

Named after the winged messenger of the gods, Mercury is the closest planet to our Sun. It’s also the smallest (now that Pluto is no longer considered a planet. At 4,879 km, it is actually smaller than the Jovian moon of Ganymede and Saturn’s largest moon, Titan.

Because of its slow rotation and tenuous atmosphere, the planet experiences extreme variations in temperature – ranging from -184 °C on the dark side and 465 °C on the side facing the Sun. Because of this, its surface is barren and sun-scorched, as seen in the image above provided by the MESSENGER spacecraft.

*A radar view of Venus taken by the Magellan spacecraft, with some gaps filled in by the Pioneer Venus orbiter. Credit: NASA/JPL*

Venus is the second planet from our Sun, and Earth’s closest neighboring planet. It also has the dubious honor of being the hottest planet in the Solar System. While farther away from the Sun than Mercury, it has a thick atmosphere made up primarily of carbon dioxide, sulfur dioxide and nitrogen gas. This causes the Sun’s heat to become trapped, pushing average temperatures up to as high as 460°C. Due to the presence of sulfuric and carbonic compounds in the atmosphere, the planet’s atmosphere also produces rainstorms of sulfuric acid.

Because of its thick atmosphere, scientists were unable to examine of the surface of the planet until 1970s and the development of radar imaging. Since that time, numerous ground-based and orbital imaging surveys have produced information on the surface, particularly by the Magellan spacecraft (1990-94). The pictures sent back by Magellan revealed a harsh landscape dominated by lava flows and volcanoes, further adding to Venus’ inhospitable reputation.

*Earth viewed from the Moon by the Apollo 11 spacecraft. Credit: NASA*

Earth is the third planet from the Sun, the densest planet in our Solar System, and the fifth largest planet. Not only is 70% of the Earth’s surface covered with water, but the planet is also in the perfect spot – in the center of the hypothetical habitable zone – to support life. It’s atmosphere is primarily composed of nitrogen and oxygen and its average surface temperatures is 7.2°C. Hence why we call it home.

Being that it is our home, observing the planet as a whole was impossible prior to the space age. However, images taken by numerous satellites and spacecraft – such as the Apollo 11 mission, shown above – have been some of the most breathtaking and iconic in history.

The first true-colour image of Mars from ESA’s Rosetta generated using the OSIRIS orange (red), green and blue colour filters. The image was acquired on 24 February 2007 at 19:28 CET from a distance of about 240 000 km. Credit: MPS for OSIRIS Team MPS/UPD/LAM/ IAA/ RSSD/ INTA/ UPM/ DASP/ IDA — *The first true-colour image of Mars taken by the ESA’s Rosetta spacecraft on 24 February 2007. Credit: MPS for OSIRIS Team MPS/UPD/LAM/ IAA/ RSSD/ INTA/ UPM/ DASP/ IDA*

Mars is the fourth planet from our Sun and Earth’s second closest neighbor. Roughly half the size of Earth, Mars is much colder than Earth, but experiences quite a bit of variability, with temperatures ranging from 20 °C at the equator during midday, to as low as -153 °C at the poles. This is due in part to Mars’ distance from the Sun, but also to its thin atmosphere which is not able to retain heat.

Mars is famous for its red color and the speculation it has sparked about life on other planets. This red color is caused by iron oxide – rust – which is plentiful on the planet’s surface. It’s surface features, which include long “canals”, have fueled speculation that the planet was home to a civilization.

Observations made by satellites flybys in the 1960’s (by the Mariner 3 and 4 spacecraft) dispelled this notion, but scientists still believe that warm, flowing water once existed on the surface, as well as organic molecules. Since that time, a small army of spacecraft and rovers have taken the Martian surface, and have produced some of the most detailed and beautiful photos of the planet to date.

Jupiter's Great Red Spot and Ganymede's Shadow. Image Credit: NASA/ESA/A. Simon (Goddard Space Flight Center) — *Jupiter’s Great Red Spot and Ganymede’s Shadow. Image Credit: NASA/ESA/A. Simon (Goddard Space Flight Center)*

Jupiter, the closest gas giant to our Sun, is also the largest planet in the Solar System. Measuring over 70,000 km in radius, it is 317 times more massive than Earth and 2.5 times more massive than all the other planets in our Solar System combined. It also has the most moons of any planet in the Solar System, with 67 confirmed satellites as of 2012.

Despite its size, Jupiter is not very dense. The planet is comprised almost entirely of gas, with what astronomers believe is a core of metallic hydrogen. Yet, the sheer amount of pressure, radiation, gravitational pull and storm activity of this planet make it the undisputed titan of our Solar System.

Jupiter has been imaged by ground-based telescopes, space telescopes, and orbiter spacecraft. The best ground-based picture was taken in 2008 by the ESO’s Very Large Telescope (VTL) using its Multi-Conjugate Adaptive Optics Demonstrator (MAD) instrument. However, the greatest images captured of the Jovian giant were taken during flybys, in this case by the Galileo and Cassini missions.

Saturn and its rings, as seen from above the planet by the Cassini spacecraft. Credit: NASA/JPL/Space Science Institute. Assembled by Gordan Ugarkovic. — *Saturn and its rings, as seen from above the planet by the Cassini spacecraft. Credit: NASA/JPL/Space Science Institute/Gordan Ugarkovic*

Saturn, the second gas giant closest to our Sun, is best known for its ring system – which is composed of rocks, dust, and other materials. All gas giants have their own system of rings, but Saturn’s system is the most visible and photogenic. The planet is also the second largest in our Solar System, and is second only to Jupiter in terms of moons (62 confirmed).

Much like Jupiter, numerous pictures have been taken of the planet by a combination of ground-based telescopes, space telescopes and orbital spacecraft. These include the Pioneer, Voyager, and most recently, Cassini spacecraft.

Uranus, seen by Voyager 2. Image credit: NASA/JPL — *Uranus, seen by Voyager 2 spacecraft. Image credit: NASA/JPL*

Another gas giant, Uranus is the seventh planet from our Sun and the third largest planet in our Solar System. The planet contains roughly 14.5 times the mass of the Earth, but it has a low density. Scientists believe it is composed of a rocky core that is surrounded by an icy mantle made up of water, ammonia and methane ice, which is itself surrounded by an outer gaseous atmosphere of hydrogen and helium.

It is for this reason that Uranus is often referred to as an “ice planet”. The concentrations of methane are also what gives Uranus its blue color. Though telescopes have captured images of the planet, only one spacecraft has even taken pictures of Uranus over the years. This was the Voyager 2 craft which performed a flyby of the planet in 1986.

Neptune from Voyager 2. Image credit: NASA/JPL

Neptune is the eight planet of our Solar System, and the farthest from the Sun. Like Uranus, it is both a gas giant and ice giant, composed of a solid core surrounded by methane and ammonia ices, surrounded by large amounts of methane gas. Once again, this methane is what gives the planet its blue color. It is also the smallest gas giant in the outer Solar System, and the fourth largest planet.

All of the gas giants have intense storms, but Neptune has the fastest winds of any planet in our Solar System. The winds on Neptune can reach up to 2,100 kilometers per hour, and the strongest of which are believed to be the Great Dark Spot, which was seen in 1989, or the Small Dark Spot (also seen in 1989). In both cases, these storms and the planet itself were observed by the Voyager 2 spacecraft, the only one to capture images of the planet.

Universe Today has many interesting articles on the subject of the planets, such as interesting facts about the planets and interesting facts about the Solar System.

If you are looking for more information, try NASA’s Solar System exploration page and an overview of the Solar System.

Astronomy Cast has episodes on all of the planets including Mercury.

January 13, 2015December 23, 2015 by Elizabeth Howell

What Other Worlds Have We Landed On?

As of November 2014, these are all of the planetary, lunar and small body surfaces where humanity has either lived, visited, or sent probes to. Composition by Mike Malaska, updated by Michiel Straathof. Image credits: Comet 67P/C-G [Rosetta/Philae]: ESA / Rosetta / Philae / CIVA / Michiel Straathof. Asteroid Itokawa [Hayabusa]: ISAS / JAXA / Gordan Ugarkovic. Moon [Apollo 17]: NASA. Venus [Venera 14]: IKI / Don Mitchell / Ted Stryk / Mike Malaska. Mars [Mars Exploration Rover Spirit]: NASA / JPL / Cornell / Mike Malaska. Titan [Cassini-Huygens]: ESA / NASA / JPL / University of Arizona. Earth: Mike Malaska

Think of all the different horizons humans have viewed on other worlds. The dust-filled skies of Mars. The Moon’s inky darkness. Titan’s orange haze. These are just a small subset of the worlds that humans or our robots landed on since the Space Age began.

It’s a mighty tribute to human imagination and engineering that we’ve managed to get to all these places, from moons to planets to comets and asteroids. By the way, for the most part we are going to focus on “soft landings” rather than impacts — so, for example, we wouldn’t count Galileo’s death plunge into Jupiter in 2003, or the series of planned landers on Mars that ended up crashing instead.

The Moon

Al Shepard raises the American flag during Apollo 14 in February 1971. Below is the shadow of his crewmate, Ed Mitchell. Credit: NASA

Our instant first association with landings on other worlds is the human landings on the Moon. While it looms large in NASA folklore, the Apollo landings only took place in a brief span of space history. Neil Armstrong and Buzz Aldrin were the first crew (on Apollo 11) to make a sortie in 1969, and Apollo 17’s Gene Cernan and Jack Schmitt made the final set of moonwalks in 1972. (Read more: How Many People Have Walked on the Moon?)

But don’t forget all the robotic surveyors that came before and after. In 1959, the Soviet Union’s Luna 2 made the first impact on the lunar surface; the first soft landing came in 1966, with Luna 9. The United States set a series of Ranger and Surveyor probes to reach the moon in the 1960s and 1970s. The Soviet Union also deployed a rover on the moon, Lunakhod 1, in 1970 — the first remote-controlled robot controlled on another world’s surface.

In 2013, China made the first lunar soft landing in a generation. The country’s Chang’e-3 not only made it safely, but deployed the Yutu rover shortly afterwards.

Mars

Mars is a popular destination for spacecraft, but only a fraction of those machines that tried to get there actually safely made it to the surface. The first successful soft landing came on Dec. 2, 1971 when the Soviet Union’s Mars 3 made it to the surface. The spacecraft, however, only transmitted for 20 seconds — perhaps due to dust storms on the planet’s surface.

Less than five years later, on July 20, 1976, NASA’s Viking 1 touched down on Chryse Planitia. This was quickly followed by its twin Viking 2 in September. NASA has actually made all the other soft landings to date, and expanded its exploration by using rovers to move around on the surface. The first one was Sojourner, a rover that rolled off the Pathfinder lander in 1997.

NASA also sent a pair of Mars Exploration Rovers in 2004. Spirit transmitted information back to Earth until 2010, while Opportunity is still roaming the surface. The more massive Curiosity lander followed them in 2012. Another stationary spacecraft, Phoenix, successfully landed close to the planet’s north pole in 2008.

Venus

Venera 7 — one of a series of Soviet probes sent in the 1960s and 1970s — was the first to make it to the surface of Venus and send data back, on Dec. 15, 1970. It lasted 23 minutes on the surface, transmitting weakly towards Earth. This may have been because it came to rest on its side after bouncing through a landing.

The first pictures of the surface came courtesy of Venera 9, which made it to Venus on Oct. 22, 1975 and sent data back for 53 minutes. Venera 10 also successfully landed three days later and sent back data from Venus as planned. Several other Venera probes followed, most notably including Venera 13 — which sent back the first color images and remained active for 127 minutes.

Titan

Humanity’s first and only landing on Titan so far came on Jan. 14, 2005. The European Space Agency’s Huygens probe likely didn’t come to rest right away when it arrived on the surface, bouncing and skidding for about 10 seconds after landing, an analysis showed almost a decade later.

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 — 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

The probe managed to send back information all the way through its 2.5-hour descent, and continued transmitting data for an hour and 12 minutes after landing. Besides the pictures, it also sent back information about the moon’s wind and surface.

The orangey moon of Saturn has come under scrutiny because it is believed to have elements in its atmosphere and on its surface that are precursors to life. It also has lakes of ethane and methane on its surface, showing that it has a liquid cycle similar to our own planet.

Comets and asteroids

Images from the Rosetta spacecraft show Philae drifting across the surface of its target comet during landing Nov. 12, 2014. Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

Robots have also touched the ground on smaller, airless bodies in our Solar System — specifically, a comet and two asteroids. NASA’s NEAR Shoemaker made the first landing on asteroid Eros on Feb. 12, 2001, even though the spacecraft wasn’t even designed to do so. While no images were sent back from the surface, it did transmit data successfully for more than two weeks.

Japan made its first landing on an extraterrestrial surface on Nov. 19, 2005, when the Hayabusa spacecraft successfully touched down on asteroid Itokawa. (This followed a failed attempt to send a small hopper/lander, called Minerva, from Hayabusa on Nov. 12.) Incredibly, Hayabusa not only made it to the surface, but took off again to return the samples to Earth — a feat it accomplished successfully in 2010.

The first comet landing came on Nov. 12, 2014 when the European Space Agency’s Philae lander successfully separated from the Rosetta orbiter and touched the surface of Comet 67P/Churyumov–Gerasimenko. Philae’s harpoons failed to deploy as planned and the lander drifted for more than two hours from its planned landing site until it stopped in a relatively shady spot on the comet’s surface. Its batteries drained after a few days and the probe fell silent. As of early 2015, controllers are hoping that as more sunlight reaches 67P by mid-year, Philae will wake up again.

January 10, 2015December 23, 2015 by Bob King

Mercury and Venus an Awesome Duo at Dusk

You couldn't miss Mercury and Venus together last night January 9th 45 minutes after sunset in the southwestern sky. Very easy to see! They'll be even closer tonight. Credit: Bob King

As Universe Today’s Dave Dickinson described earlier this week not only has Venus returned to the evening sky, but Mercury has climbed up from the horizon to join it. Last night (Jan. 9th) the two planets were separated by just a hair more than one Moon diameter. The photo only hints at amazingly easy the pair was to see. Consider the duo a tasty hors d’oeuvres before the onset of night and the Comet Lovejoy show.

Tonight the duo will be at their closest and remain near one another for the next week or so. This is one of Mercury’s best apparitions of the year for northern hemisphere skywatchers and well worth donning your winter uniform of coat, boots, hat and thick gloves for a look. Just find a location with a decent view of the southwestern horizon and start looking about a half hour after sunset. Mercury and Venus will be about 10° or one fist held at arm’s length high above the horizon.

Through a telescope both Venus and Mercury are in gibbous phase with Venus more fully filled out. Both are also very small with Venus about 10 arc seconds and Mercury 6 seconds across. Source: Stellarium — Through a telescope both Venus and Mercury are in gibbous phase with Venus more fully filled out. Both are very small with Venus about 10 arc seconds in diameter and Mercury 6 seconds. Source: Stellarium

Venus will jump right out. Mercury’s a couple magnitudes fainter and lies to the right of the goddess planet. By 45 minutes after sunset, Mercury gets even easier to see. Find your sunset time HERE so you can best plan your outing.

Mark your calendars for a cool conjunction of the 1-day-old lunar crescent, Mercury and Venus on January 21st. Source: Stellarium

Because both planets are still fairly low in the sky and far away, they present only tiny, blurry gibbous disks in the telescope. Later this spring, Venus will climb higher and show its changing phases more clearly. Keep watch the coming week to catch the ever-shifting positions of Venus and Mercury in the evening sky as each follows the binding arc of its own orbit. The grand finale occurs on January 21st when a skinny crescent Moon joins the duo (Mercury now fading) for a triumphant trio. Has this been an exciting month or what?

January 6, 2015December 23, 2015 by Matt Williams

Japan’s Akatsuki Spacecraft to Make Second Attempt to Enter Orbit of Venus in December 2015

Artist’s impression of the Venus Climate Orbiter (aka. “Akatsuki”) by Akihiro Ikeshita. Image Credit: JAXA

Back in 2010, the Japanese Aerospace Exploration Agency (JAXA) launched the The Venus Climate Orbiter “Akatsuki” with the intention of learning more about the planet’s weather and surface conditions. Unfortunately, due to engine trouble, the probe failed to make it into the planet’s orbit.

Since that time, it has remained in a heliocentric orbit, some 134 million kilometers from Venus, conducting scientific studies on the solar wind. However, JAXA is going to make one more attempt to slip the probe into Venus’ orbit before its fuel runs out.

Since 2010, JAXA has been working to keep Akatsuki functioning so that they could give the spacecraft another try at entering Venus’ orbit.

After a thorough examination of all the possibilities for the failure, JAXA determined that the probe’s main engine burned out as it attempted to decelerate on approach to the planet. They claim this was likely due to a malfunctioning valve in the spacecraft’s fuel pressure system caused by salt deposits jamming the valve between the helium pressurization tank and the fuel tank. This resulted in high temperatures that damaged the engine’s combustion chamber throat and nozzle.

JAXA adjusted the spacecraft’s orbit so that it would establish a heliocentric orbit, with the hopes that it would be able to swing by Venus again in the future. Initially, the plan was to make another orbit insertion attempt by the end 2016 when the spacecraft’s orbit would bring it back to Venus. But because the spacecraft’s speed has slowed more than expected, JAXA determined if they slowly decelerated Akatsuki even more, Venus would “catch up with it” even sooner. A quicker return to Venus would also be advantageous in terms of the lifespan of the spacecraft and its equipment.

But this second chance will likely be the final chance, depending on how much damage there is to the engines and other systems. The reasons for making this final attempt are quite obvious. In addition to providing vital information on Venus’ meteorological phenomena and surface conditions, the successful orbital insertion of Akatsuki would also be the first time that Japan deployed a satellite around a planet other than Earth.

If all goes well, Akatsuki will enter orbit around Venus at a distance of roughly 300,000 to 400,000 km from the surface, using the probe’s 12 smaller engines since the main engine remains non-functional. The original mission called for the probe to establish an elliptical orbit that would place it 300 to 80,000 km away from Venus’ surface.

This wide variation in distance was intended to provide the chance to study the planet’s meteorological phenomena and its surface in detail, while still being able to observe atmospheric particles escaping into space.

Artist's impression of Venus Express entering orbit in 2006. Credit: ESA - AOES Medialab — *Artist’s impression of Venus Express entering orbit in 2006. Image Credit: ESA – AOES Medialab*

At a distance of 400,000 km, the image quality and opportunities to capture them are expected to be diminished. However, JAXA is still confident that it will be able to accomplish most of the mission’s scientific goals.

In its original form, these goals included obtaining meteorological information on Venus using four cameras that capture images in the ultraviolet and infrared wavelengths. These would be responsible for globally mapping clouds and peering beneath the veil of the planet’s thick atmosphere.

Lightning would be detected with a high-speed imager, and radio-science monitors would observe the vertical structure of the atmosphere. In so doing, JAXA hopes to confirm the existence of surface volcanoes and lighting, both of which were first detected by the ESA’s Venus Express spacecraft. One of the original aims of Akatsuki was to complement the Venus Express mission. But Venus Express has now completed its mission, running out of gas and plunging into the planet’s atmosphere.

But most of all, it is hoped that Akatsuki can provide observational data on the greatest mystery of Venus, which has to do with its surface storms.

*Artists impression of lightning storms on Venus. Credit: ESA*

Previous observations of the planet have shown that winds that can reach up to 100 m/s (360 km/h or ~225 mph) circle the planet every four to five Earth days. This means that Venus experiences winds that are up to 60 times faster than the speed at which the planet turns, a phenomena known as “Super-rotation”.

Here on Earth, the fastest winds are only capable of reaching between 10 and 20 percent of the planet’s rotation. As such, our current meteorological understanding does not account for these super-high speed winds, and it is hoped that more information on the atmosphere will provide some clues as to how this can happen.

Between the extremely thick clouds, sulfuric rain storms, lightning, and high-speed winds, Venus’ atmosphere is certainly very interesting! Add to the fact that the volcanic, pockmarked surface cannot be surveyed without the help of sophisticated radar or IR imaging, and you begin to understand why JAXA is eager to get their probe into orbit while they still can.

And be sure to check out this video, courtesy of JAXA, detailing the Venus Climate Orbiter mission:

Further Reading: JAXA

December 23, 2014December 23, 2015 by Matt Williams

What is the Average Surface Temperature on Venus?

Venus is often referred to as our “sister planet,” due to the many geophysical similarities that exist between it Earth. For starters, our two planets are close in mass, with Venus weighing in at 4.868 x 10²⁴ kg compared to Earth’s 5.9736×10²⁴kg. In terms of size, the planets are almost identical, with Venus measuring 12,100 km in diameter and Earth 12,742 km.

In terms of density and gravity, the two are neck and neck – with Venus boasting 86.6% of the former and 90.7% of the latter. Venus also has a thick atmosphere, much like our own, and it is believed that both planets share a common origin, forming at the same time out of a condensing clouds of dust particles around 4.5 billion years ago.

However, for all the characteristics these two planets have in common, average temperature is not one of them. Whereas the Earth has an average surface temperature of 14 degrees Celsius, the average temperature of Venus is 460 degrees Celsius. That is roughly 410 degrees hotter than the hottest deserts on our planet.

In fact, at a searing 750 K (477 °C), the surface of Venus is the hottest in the solar system. Venus is closer to the Sun by 108 million km, (about 30% closer than the Earth), but it is mainly due to the planet’s thick atmosphere. Unlike Earth’s, which is composed primarily of nitrogen, oxygen and ozone, Venus’ atmosphere is an incredibly dense cloud of carbon dioxide and sulfur dioxide gas.

The combination of these gases in high concentrations causes a catastrophic greenhouse effect that traps incident sunlight and prevents it from radiating into space. This results in an estimated surface temperature boost of 475 K (201.85 °C), leaving the surface a molten, charred mess that nothing (that we know of) can live on. Atmospheric pressure also plays a role, being 91 times that of what it is here on Earth; and clouds of toxic vapor constantly rain sulfuric acid on the surface.

In addition, the surface temperature on Venus does not vary like it does here on Earth. On our planet, temperatures vary wildly due to the time of year and even more so based on the location on our planet. The hottest temperature ever recorded on Earth was 70.7°C in the Lut Desert of Iran in 2005. On the other end of the spectrum, the coldest temperature ever recorded on Earth was in Vostok, Antarctica at -89.2 C.

But on Venus, the surface temperature is 460 degrees Celsius, day or night, at the poles or at the equator. Beyond its thick atmosphere, Venus’ axial tilt (aka. obliquity) plays a role in this temperature consistency. Earth’s axis is tilted 23.4 ° in relation to the Sun, whereas Venus’ is only tilted by 3 °.

The only respite from the heat on Venus is to be found around 50 km into the atmosphere. It is at that point that temperatures and atmospheric pressure are equal to that of Earth’s. It is for this reason that some scientists believe that floating habitats could be constructed here, using Venus’ thick clouds to buoy the habitats high above the surface. Additionally, in 2014, a group of mission planners from NASA Langely came up with a mission to Venus’ atmosphere using airships.

These habitats could play an important role in the terraforming of Venus as well, acting as scientific research stations that could either fire off the excess atmosphere off into space, or introduce bacteria or chemicals that could convert all the CO2 and SO2 into a hospitable, breathable atmosphere.

Beyond the fact that it is a hot and hellish landscape, very little is known about Venus’ surface environment. This is due to the thick atmosphere, which has made visual observation impossible. The sulfuric acid is also problematic since clouds composed of it are highly reflective of visible light, which prevents optical observation. Probes have been sent to the surface in the past, but the volatile and corrosive environment means that anything that lands there can only survive for a few hours.

*3-D perspective of the Venusian volcano, Maat Mons generated from radar data from NASA’s Magellan mission. Credit: Magellan Team/NASA/JPL*

What little we know about the planet’s surface has come from years worth of radar imaging, the most recent of which was conducted by NASA’s Magellan spacecraft (aka. the Venus Radar Mapper). Using synthetic aperture radar, the robotic space probe spent four years (1990-1994) mapping the surface of Venus and measuring its gravitational field before its orbit decayed and it was “disposed of” in the planet’s atmosphere.

The images provided by this and other missions revealed a surface dominated by volcanoes. There are at least 1,000 volcanoes or volcanic centers larger than 20 km in diameter on Venus’ harsh landscape. Many scientists believe Venus was resurfaced by volcanic activity 300 to 500 million years ago. Lava flows are a testament to this, which appear to have produced channels of hardened magma that extend for hundreds of km in all directions. The mixture of volcanic ash and the sulfuric acid clouds is also known to produce intense lightning and thunder storms.

The temperature of Venus is not the only extreme on the planet. The atmosphere is constantly churned by hurricane force winds reaching 360 kph. Add to that the crushing air pressure and rainstorms of sulfuric acid, and it becomes easy to see why Venus is such a barren, lifeless rock that has been hard to explore.

We have written many articles about Venus for Universe Today. Here are some interesting facts about Venus, and here’s an article about Venus Greenhouse Effect. And here is an article about the many interesting pictures taken of Venus over the past few decades.

If you’d like more information on Venus, check out Hubblesite’s News Releases about Venus, and here’s a link to NASA’s Solar System Exploration Guide on Venus.

We’ve also recorded an entire episode of Astronomy Cast all about Venus. Listen here, Episode 50: Venus.

Reference:
NASA

December 18, 2014March 1, 2017 by Fraser Cain

Why Is Venus So Horrible?

Venus really sucks. It’s as hot as an oven with a dense, poisonous atmosphere. But how did it get that way?

Venus sucks. Seriously, it’s the worst. The global temperature is as hot as an oven, the atmospheric pressure is 90 times Earth, and it rains sulfuric acid. Every part of the surface of Venus would kill you dead in moments.

Let’s push Venus into the Sun and be done with that terrible place. Its proximity is lowering our real estate values and who knows what sort of interstellar monstrosities are going to set up shop there, and be constantly knocking on our door to borrow the mower, or a cup or sugar, or sneak into our yard at night and eat all our dolphins.

You might argue that Venus is worth saving because it’s located within the Solar System’s habitable zone, that special place where water could exist in a liquid state on the surface. But we’re pretty sure it doesn’t have any liquid water. Venus may have been better in the past, clearly it started hanging out with wrong crowd, taking a bad turn down a dark road leading it to its current state of disrepair.

Could Venus have been better in the past? And how did it go so wrong? In many ways, Venus is a twin of the Earth. It’s almost the same size and mass as the Earth, and it’s made up of roughly the same elements. And if you stood on the surface of Venus, in the brief moments before you evacuated your bowels and died horribly, you’d notice the gravity feels pretty similar.

In the ancient past, the Sun was dimmer and cooler than it is now. Cool enough that Venus was much more similar to Earth with rivers, lakes and oceans. NASA’s Pioneer spacecraft probed beneath the planet’s thick clouds and revealed that there was once liquid water on the surface of Venus. And with liquid water, there could have been life on the surface and in those oceans.

Here’s where Venus went wrong. It’s about a third closer to the Sun than Earth, and gets roughly double the solar radiation. The Sun has been slowly heating up over the millions and billions of years. At some point, the planet reached a tipping point, where the water on the surface of Venus completely evaporated into the atmosphere.

Water vapor is a powerful greenhouse gas, and this only increased the global temperature, creating a runaway greenhouse effect on Venus. The ultraviolet light from the Sun split apart the water vapor into oxygen and hydrogen. The hydrogen was light enough to escape the atmosphere of Venus into space, while the oxygen recombined with carbon to form the thick carbon dioxide atmosphere we see today. Without that hydrogen, Venus’ water is never coming back.

Are you worried about our changing climate doing that here? Don’t panic. The amount of carbon dioxide released into the atmosphere of Venus is incomprehensible. According to the IPCC, the folks studying global warming, human activities have no chance of unleashing runaway global warming. We’ll just have the regular old, really awful global warming. So, it’s okay to panic a bit, but do it in the productive way that results in your driving your car less.

The Sun is still slowly heating up. And in a billion years or so, temperatures here will get hot enough to boil the oceans away. And then, Earth and Venus will be twins again and then we can push them both into the Sun.

I know, I said the words “climate change”. Feel free to have an argument in the comments below, but play nice and bring science.