Mercury | Universe Today

Compared to Earth, Mercury doesn't have much of an atmosphere.  The smallest rocky planet has weak surface gravity, only 38% that of Earth.  And the scorching-hot daytime surface temperatures of 800 degrees Fahrenheit (approximately 450 degrees Celsius) should have boiled away any trace of Mercury's atmosphere long ago.  Yet recent flybys of the MESSENGER spacecraft clearly revealed Mercury somehow retains a thin layer of gas near its surface.   Where does this atmosphere come from?

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Making good on its promise to work together with other space agencies, NASA has selected two science instruments that will fly on board European Space Agency (ESA) spacecraft, one heading to Mars on the ExoMars rover, the other to Mercury with the BepiColombo orbiter. "The selections will further advance our knowledge of these exciting terrestrial planets," said Jim Green, director of NASA's Planetary Division at NASA Headquarters in Washington. "The international collaboration will create a new chapter in planetary science and provide a strong partnership with the international science community to complement future robotic and human exploration activities."
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Even though Mercury looks like the Moon at first glance, scientists from the MESSENGER mission say it's becoming apparent that Mercury is an amazingly dynamic planet, and is actually more like Mars. For example, before this mission, scientists weren't sure if volcanism even existed on Mercury, but from the spacecraft's two flybys, they now know it is a very important part of the planet's history. Additional new findings from the second flyby of Mercury in October 2008 show that the planet’s atmosphere, magnetosphere, and geological past are all characterized by much greater levels of activity than scientists first suspected.

And by the way, isn't this a stunning picture of an impact basin? It's one of the new discoveries from MESSENGER.
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Scientists from the MESSENGER mission to Mercury discussed today the results from the spacecraft's October 6 flyby of the closest planet to the sun. The probe has produced several science firsts and is returning hundreds of new photos and measurements of the planet's surface, atmosphere and magnetic field. The images show a battered surface, and we now have pictures and data of parts of Mercury's surface that have never been examined by a spacecraft. "The region of Mercury's surface that we viewed at close range for the first time this month is bigger than the land area of South America," said Sean Solomon, principal investigator and director of the Department of Terrestrial Magnetism at the Carnegie Institution of Washington. "When combined with data from our first flyby and from Mariner 10, our latest coverage means that we have now seen about 95 percent of the planet."
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Here's the first image from MESSENGER's flyby of Mercury on Monday. The bright crater just south of the center of the image is Kuiper, which has been seen before on images from the Mariner 10 mission in the 1970s. But most of this image, to the east, or right of Kuiper, toward the limb of Mercury is new territory for human eyes – at least in optical views. The image was taken by the Wide Angle Camera as MESSENGER was departing from the planet, and are among the first spacecraft views of that portion of Mercury’s surface. Most striking are the large pattern of rays that extend from north to south, almost along the entire face of Mercury. Amazing! This extensive ray system appears to emanate from a relatively young crater newly imaged by MESSENGER, providing a view of the planet distinctly unique from that obtained during MESSENGER’s first flyby.

2nd Update: (9:40 am CDT) More images!

Update: (8:50 am CDT) See 2nd image released below:

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This morning at 4:40 am EDT, the MESSENGER spacecraft passed only 200 kilometers (124 miles) above Mercury’s surface as it made its second flyby of the mission. Now, the spacecraft is speeding away from Mercury, continuing its science observations for about 20 hours following closest approach. This flyby should provide the first global perspective of Mercury, as, if all went well, we should have images in total covering about 95 percent of the planet. "This second flyby will show us a completely new area of Mercury's surface, opposite from the side of the planet we saw during the first," said Louise M. Prockter, scientist for the mission.

If you're looking for images and data from the flyby here, sorry to disappoint, but data will be transmitted to Earth only after the completion of all science observations. So, for now, even the MESSENGER science team has to wait. But scientists are already eagerly exploring the optical navigation images acquired just prior to the flyby. Shown here is a Narrow Angle Camera (NAC) image from the eighth and final optical navigation image set, taken about 14.5 hours before the flyby’s closest approach.
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Scientists from the MESSENGER mission continue to analyze the data from the spacecraft's first flyby of Mercury on January 14, 2008. Initial data about the planet's gravity field grabbed the science team's attention, as the actual gravity data differed from predictions based on the Mariner 10 flyby in 1975. Any unknowns in Mercury's gravity will provide challenges for the spacecraft's navigation during the next flyby in October, and especially when MESSENGER goes into orbit of Mercury in 2011. This in turn could affect quality and detail of science observations. "There indeed are residuals that we have not yet been able to explain fully," said Ralph McNutt, MESSENGER Project Scientist. "While we believe we have resolved possible extraneous effects, we continue to work those as well."
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No, not that kind of snow, but scientists say deep inside the planet Mercury, iron “snow” forms and falls toward the center of the planet, much like snowflakes form in Earth’s atmosphere and fall to the ground. The movement of this iron snow could be responsible for Mercury’s mysterious magnetic field, and Mercury may be the only body in our solar system where this occurs.
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Scientists have expressed their concern that the Solar System may not be as stable as it seems. Happily orbiting the Sun, the eight planets (plus Pluto and other minor planets) appear to have a high degree of long-term gravitational stability. But Jupiter has a huge gravitational influence over its siblings, especially the smaller planets. It appears that the long-term prospects for the smallest planet are bleak. The huge gravitational pull of Jupiter seems to be bullying Mercury into an increasingly eccentric death-orbit, possibly flinging the cosmic lightweight into the path of Venus. To make things worse, there might be dire consequences for Earth…
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With Mercury fading in MESSENGER's rear view mirror, scientists are just starting to pore through the torrent of images sent back. And as you can probably guess, the new mysteries are piling up fast and furious. The planet is much less like the Moon than scientists previously thought.
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The MESSENGER science team released more pictures from the Jan. 14 flyby, including what we’ve all been waiting for, the first one in color! But if you're looking for spectacular, eye-catching color, well, sorry, its just not part of Mercury's make-up.

The color image was created by combining three separate images taken through MESSENGER’s Wide Angle Camera (WAC) filters in the infrared, far red, and violet wavelengths (red, green, and blue filters for this image.) MESSENGER’s eyes can see far beyond the color range of the human eye, and the colors seen in this image are somewhat different from what a human would see.

Creating a false-color image in this way brings out color differences on Mercury's surface that cannot be seen in the black and white images released earlier.
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British scientists have been given the green light to begin the development of the most advanced ion engines ever to be used in space travel history. Set for launch in 2013, the European/Japanese BepiColombo mission to Mercury will be propelled to the Solar System's innermost planet by advanced ion engines, with an efficiency equivalent to 17.8 million miles per gallon. This is one very cheap spaceship to fly!
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Even though the Mercury flyby happened earlier this week, you can look forward to days and days of images. I'm nowhere near finished being amazed and entertained by the deluge of images captured by MESSENGER.
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Even though spacecraft have visited Mercury in the past, the same hemisphere was always in sunlight for every encounter. One side was photographed, and the other side was a complete and total mystery. There could be a big smiley face there, and we'd never know it. Well, the mystery's over. MESSENGER flew past Mercury on January 14th, 2008, and revealed the planet's hidden side… mostly.
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On January 14 the MESSENGER spacecraft skimmed just 200 kilometers (124 miles) above the surface of Mercury in the first of three flybys of the planet. Today (Jan. 15) the spacecraft will turn back towards the Earth to start down-linking the on-board stored science data it acquired during the flyby. The probe's equipment gathered data on the mineral and chemical composition of Mercury's surface, its magnetic field, its surface topography and its interactions with the solar wind. "This was fantastic," said Michael Paul, a mission engineer. "We were closer to the surface of Mercury than the International Space Station is to the Earth."
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