Phobos flyby season starts again

February 16, 2010
Artist's impression of Mars Express. Credits: Alex Lutkus

( -- Today Mars Express began a series of flybys of Phobos, the largest moon of Mars. The campaign will reach its crescendo on 3 March, when the spacecraft will set a new record for the closest pass to Phobos, skimming the surface at just 50 km. The data collected could help untangle the origin of this mysterious moon.

The latest Phobos flyby campaign began today at 06:52 CET (05:52 UT), when drew to within 991 km of Phobos’ airless surface. The flybys will continue at varying altitudes until 26 March when Phobos moves out of range. They offer prime chances for doing additional science with Mars Express, a spacecraft that was designed to study the below rather than the grey moon alongside.

“Because Mars Express is in an elliptical and with a maximum distance from Mars of about 10 000 km, we regularly pass Phobos. This represents an excellent opportunity to perform extra science,” says Olivier Witasse, Mars Express Project Scientist.
Back in 2009, the mission team decided that the orbit of Mars Express needed to be adjusted to prevent the closest approach of the spacecraft drifting onto the planet’s nightside. The flight control team at the European Space Operations Centre in Darmstadt, Germany, presented a number of possible scenarios, including one that would take the spacecraft to just 50 km above Phobos. “That was the closest they would let us fly to Phobos,” says Witasse.

This video is not supported by your browser at this time.
This animation shows the 3D (shape) model of Mars’ moon Phobos, built thanks to the data collected by Mars Express’ High Resolution Stereo Camera (53 images obtained by the Super Resolution Channel, or SRC) and NASA’s Viking (16 images). The model is dressed with a mosaic of the same images. The SRC coverage is about 70% of the moon’s surface. The mean resolution is 12 m/pixel. Credits: ESA/ DLR (K.Willner)/ FU Berlin (G. Neukum)

Precise gravity measurements

Heavy emphasis is being placed upon the closest flyby because it is an unprecedented opportunity to map Phobos’ . At that range, Mars Express should feel differences in the pull from Phobos depending which part of the moon is closest at the time. This will allow scientists to infer the moon’s internal structure.

Previous Mars Express flybys have already provided the most accurate mass yet for Phobos, and the (HRSC) has provided the volume. When calculating the density, this gives a surprising figure because it seems that parts of Phobos may be hollow. The science team aim to verify this preliminary conclusion.

In particular, the MARSIS radar will operate in a special sequence to try to see inside the moon, looking for structures or some clue to the internal composition. “If we know more about how Phobos is built, we might know more about how it formed,” says Witasse.

The origin of Phobos is a mystery. Three scenarios are possible. The first is that the is a captured asteroid. The second is that it formed in situ as Mars formed below it. The third is that Phobos formed later than Mars, out of debris flung into Martian orbit when a large meteorite struck the red planet.

All the instruments will be used during the campaign, including HRSC. Although no imaging will be possible during the first five flybys, including the closest one, because Express approaches from the nightside, high-resolution pictures will be possible from 7 March onwards. One task for HRSC is to image the proposed landing sites for the Russian mission Phobos-Grunt.

“It is always busy,” says Witasse about running the science mission. “The flybys make it even more exciting.”

Explore further: Russia plans two new missions to Mars

Related Stories

Mars Express to rendezvous with Martian moon

July 16, 2008

( -- Scientists and engineers are preparing ESA’s Mars Express for a pair of close fly-bys of the Martian moon Phobos. Passing within 100 km of the surface, Mars Express will conduct some of the most detailed ...

Scientists close in on the origin of Mars' larger moon

October 16, 2008

( -- European space scientists are getting closer to unravelling the origin of Mars’ larger moon, Phobos. Thanks to a series of close encounters by ESA’s Mars Express spacecraft, the moon looks almost certain ...

Pioneering images of both martian moons (w/ Video)

December 11, 2009

( -- For the very first time, the martian moons Phobos and Deimos have been caught on camera together. ESA's Mars Express orbiter took these pioneering images last month. Apart from their ‘wow’ factor, these ...

Auspicious orbit marks run-up to Phobos flyby

January 29, 2010

( -- On 26 January, Mars Express completed its 7777th orbit around the Red Planet, an auspicious milestone as the satellite is readied for the closest-ever flyby of Phobos, scheduled for just a few weeks from ...

Recommended for you

Dead comets and near-earth encounters

October 13, 2015

Near Earth Objects (NEOs) are asteroids or comets whose orbits sometimes bring them close to the Earth, thereby posing a potentially threat. The asteroid that struck Chelyabinsk last year was an NEO about 40 meters in diameter. ...

What happens when your brain can't tell which way is up?

October 13, 2015

In space, there is no "up" or "down." That can mess with the human brain and affect the way people move and think in space. An investigation on the International Space Station seeks to understand how the brain changes in ...


Adjust slider to filter visible comments by rank

Display comments: newest first

not rated yet Feb 16, 2010
"Although no imaging will be possible during the first five flybys, including the closest one"

Gah! What a loss.
1 / 5 (1) Feb 16, 2010
We must go to the Moon as a 'baby step' to Mars. Goddamn the Obamination for abandoning the legacy and dream of the greatest generation.
not rated yet Feb 16, 2010
" seems that parts of Phobos may be hollow. "

They've never heard of the Hollow Phobos hypothesis?

(http://en.wikiped...gestions )

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.