Previously considered (blue) and current mission landing sites.
Credit: ESA/DLR/FU Berlin (G. Neukum)

 

Phobos-Grunt
Aug 04, 2011

A Russian space mission will attempt to land a sample return package on Phobos.

In October 2011 the Russian Space agency, RosCosmos, will launch a scientific instrument package toward Mars, with a planned landing on its largest moon in either March or April of 2013. The small lander will gather samples of the surface and then blast off for a rendezvous with an Earth return vehicle.

Phobos and Deimos are the two moons of Mars, although Deimos is so small it cannot be readily observed from Earth. Only the Viking 2 orbiter captured close up images in 1976. Phobos has been extensively studied by Earth-based telescopes and by satellites in Mars orbit.

Picture of the Day articles about Mars have shown that it was once immersed in a plasma flame sufficiently large to gouge out Valles Marineris. Millions of cubic kilometers of rock and dust were blasted out from the planet at escape velocity. Stone blocks larger than Manhattan Island fell back to Mars from a great height, shattering on impact. This explains the fields of enormous boulders with sharp edges covering millions of square kilometers. Could it be that moons like Phobos and Deimos, as well as asteroids like Ida, were also born from that cataclysm?

Stickney crater dominates one hemisphere of Phobos. It is 10 kilometers wide and more than 100 meters deep. Many previous Picture of the Day articles mention the physical problems associated with blasting large craters into small bodies. For example, there is a hole in asteroid 253 Mathilde that should have caused it to disintegrate. Phobos is a mere 28 by 20 kilometers in size, so Stickney is nearly half as big.

Scientists speculate that asteroids (and perhaps small moons) are loose aggregations of rocks and soil, similar to a gravel pit in space. Since they were not blown apart from meteor impacts, it is thought that they most likely behaved like a pile of sand, cushioning the shock. Does the gravel pile theory best fit the facts?

Since Phobos is about the same size as asteroids Mathilde, Eros and Ida, exhibiting the same features like relatively gigantic craters, is there a common event that can form similar structures without obliterating the objects in the first place? The answer is electricity.

The electrical history of the solar system includes intensely energetic events and violent interactions between charged planets and moons. That electric arcs can remove material with ease is proven by the experiments conducted by Dr. C. J. Ransom of VEMASAT Laboratories. His plasma discharges excavate surface depressions, scoop out material, and explode it into the air, leaving cleanly cut features.

The lightning bolts that carved Mars threw large chunks of its crust into orbit around it, as well as sending them around the Sun. The electric fields that accompanied the celestial disasters of the past smoothed and eroded them with plasma discharges. The result is that Phobos and the asteroids mentioned are covered in dust, are defined by huge craters, and look like they're half-melted.

Phobos and Deimos appear to be remnants of a catastrophic event that electrically devastated their parent planet.

Stephen Smith