[meteorite-list] Phobos As Dropbox for Mars Sample Return

[Ron Baalke]

http://redplanet.asu.edu/?p=4952

Phobos as dropbox for Mars sample return
by Robert Burnham
Red Planet Report
March 20, 2014

Current plans for bringing samples to Earth from Mars involve three distinct 
steps. First is a rover with the capability to cache samples: this will 
be the Mars 2020 rover, now in its initial stages of development.

Second is a special lander carrying a small 'fetch rover" that collects 
the cached samples and brings them to the lander, which then sends them 
up into Martian parking orbit. The third step sends a spacecraft to Mars 
to collect the orbiting samples and deliver them to Earth. All these are 
robotic spacecraft, and for budgetary purposes, several years could easily 
intervene between each step.

But what if the second step deposited the samples on the surface of Phobos, 
Mars' larger moon, instead of sending them into orbit around Mars or directly 
to Earth?

That's the suggestion of Philip Stooke (University of Western Ontario). 
He presented the idea (PDF) in a poster talk (PDF electronic version here) 
at the 45th Lunar and Planetary Science Conference in The Woodlands, Texas.

Using Phobos as a dropbox offers several advantages, he argues. It has 
only weak gravity, so landing a sample collection there will be easy, 
using airbags for example. Also, Phobos could serve as a place where Mars 
missions by other space agencies could drop off samples they collect.

In Stooke's scenario, a mission with a human crew would retrieve the samples 
from Phobos. This would serve as a rehearsal for a crewed landing mission 
to Mars, much as Apollo 10 was the dress rehearsal for the actual first 
lunar landing by Apollo 11.

"Human flights to Mars will be extremely risky and expensive," he says, 
"making a rehearsal mission both necessary for system testing yet hard 
to justify in scientific terms." Thus he is proposing to combine both 
sample return and rehearsal into a decade-long program of robotic sample 
collection that culminates in a human flight to Phobos to collect and 
return the samples.

An added advantage, says Stooke, is that Phobos itself is a good target 
for samples to collect. Besides original Phobos material, the moon's regolith 
is littered with rocks thrown off Mars by large impacts. The retrieval 
crew would scout for these for when they arrive to collect the samples.

Finally, he notes that parking samples on Phobos does not commit anyone 
to a crewed mission to Mars: "If human Mars exploration is eventually 
deemed impossible, a flagship-class robotic mission to Phobos can gather 
the samples instead."