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#903081 11/15/15 06:12 AM
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NASA launched its MAVEN probe to Mars on November 18, 2013. Its main mission was to find out how Mars changed from a planet with a thick atmosphere that kept it warm, and rivers, lakes and seas. Today's Mars is cold and arid with a very thin atmosphere.

Results released earlier this month show that the transformation began 4.2 billion years ago. That's when the planet's magnetic field was lost. Earth's magnetic field protects us from damaging particles from the Sun, but more importantly it prevents the solar wind from stripping away our atmosphere. Once Mars lost this protection, over a period of 500 million years, it gradually lost its atmosphere.

Once a protective atmosphere is lost, surface water evaporates and is also lost.

Here is an artist's rendering of a solar storm stripping gas particles from the Martian atmosphere.

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We have aurorae on Earth when charged particles from the Sun are funnelled down to the poles along magnetic field lines. But unlike Earth, Mars isn't a giant magnet and doesn't have a planetary magnetic field. Once upon a time it did, and some of the rocks that formed from magma at the time have remnant magnetic fields in them. These are mostly – but not exclusively – in the older surface rocks of the Martian southern hemisphere.

In 2005 the European Mars Express orbiter detected aurorae in the southern hemisphere where the magnetic remnants are. But NASA's MAVEN has detected an aurora over the northern hemisphere which lasted five days.

On Earth occasionally we're treated to lively auroral displays, but the Martian ones have been just a diffuse glow. In addition, since their detection is in the ultraviolet, we wouldn't see them even if we were on Mars.

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Mars has two small rather shapeless moons, Deimos and Phobos. They're probably captured asteroids.

The larger one, Phobos, is being slowly pulled towards Mars, though at 3-6 feet per century, we're not going to be around to get impact photos from Mars probes via social media. It's at least 30 million years in the future. But the news is that Phobos may not last that long. It looks as though Phobos is starting to fall apart, according to research presented at a recent planetary sciences meeting.

Phobos has noticeable grooves on its surface and formerly, astronomers thought they were fractures from a massive asteroid impact. It left a 6-mile wide crater, near half the width of the moon. But the new study, which has used computer modeling, proposes that the grooves are evidence of the gravitational effect of Mars. Tidal forces are pulling it apart.

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Have you seen the film "The Martian"? Or even read the book? I saw the movie today and quite enjoyed it. I understand that the book's author was very keen on authenticity and as for the movie, the Jordanian desert made a good Mars.

The spacecraft was pretty fancy - can't see NASA coming up with anything like that in the near future. And I couldn't believe in the ending. But all very watchable, with snappy dialog. Must be rather impressive in 3D.

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On the rim of Schiaparelli Crater. The picture was taken from orbit by ESA's Mars Express orbiter.

The basin was named for Italian astronomer Giovanni Schiaparelli who thought he saw "canale" on Mars, i.e., straightline features. That got translated into English as "canals" suggesting that they were artificial.

The entry, descent and landing demonstrator module of the joint ESA–Roscosmos ExoMars 2016 mission also honours the astronomer with the name Schiaparelli.

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When Mars's moon Phobos breaks up, Mars will become a ringed planet (Image: Tushar Mittal/Celestia Development Team) But it's not expected to happen for around forty million years, so I guess we're not going to see that.

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Wow! Trees and bushes on Mars! Oh. No, apparently not. They're just dark brown streaks from dark sand on the lighter pink sand. There would be shadows if the dark bits were anything upright.

Dark Sand Cascades on Mars

(Image Credit: HiRISE, MRO, LPL (U. Arizona), NASA)

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Here is a 1700 km long view taken in a south-north direction across the Valles Marineris of Mars, an enormous canyon system. It was taken by ESA's Mars Express, and is the first image of this size that shows the surface of Mars in high resolution (12 metres per pixel), in colour and in 3D.

It was taken ten years ago today on 14 January 2004.

(Copyright ESA/DLR/FU Berlin (G. Neukum))

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NASA's Curiosity rover has found much higher concentrations of silica at some sites in the past seven months than anywhere else it's been on Mars 40. Silica makes up nine-tenths of the composition of some of the rocks. Silica is a rock-forming chemical that combines silicon and oxygen. It's seen on Earth in many minerals, most commonly as quartz.

A Curiosity science team member said,
Quote:
These high-silica compositions are a puzzle. You can boost the concentration of silica either by leaching away other ingredients while leaving the silica behind, or by bringing in silica from somewhere else. Either of those processes involve water. If we can determine which happened, we'll learn more about other conditions in those ancient wet environments.


Acidic water would tend to carry other ingredients away and leave silica behind. Alkaline or neutral water could bring in dissolved silica that would be deposited from the solution. These findings on Mount Sharp are linked to what the Spirit rover found a long way away. There, signs of sulfuric acidity were observed.

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There's one Mars mission to be launched this year, the European Space Agency's ExoMars. It's due to be launched from Baikonur in Russia on a Proton rocket on March 14. It consists of two parts: the Trace Gas Orbiter (TGO) and the Sciaparelli lander which is an entry, descent and landing demonstrator module (EDL). The two parts have now been configured ready for launch. Photo Credit: ESA – B. Bethge

“The main objectives of this mission are to search for evidence of methane and other trace atmospheric gases that could be signatures of active biological or geological processes and to test key technologies in preparation for ESA’s contribution to subsequent missions to Mars,” says ESA.

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