As Curiosity continues to trek across the wild red yonder of Mars, it stopped for a moment earlier this month to observe the two Martian moons, Phobos and Deimos, passing by each other in the night sky. This imagery of one Martian moon eclipsing another as seen from the surface of Mars is the first of its kind, and serves a useful purpose for astronomers.
“The ultimate goal is to improve orbit knowledge enough that we can improve the measurement of the tides Phobos raises on the Martian solid surface, giving knowledge of the Martian interior,” said Mark Lemmon, a Texas A&M University co-investigator working with Curiosity’s Mastcam. “We may also get data good enough to detect density variations within Phobos and to determine if Deimos’ orbit is systematically changing.”

Slamming into the Martian atmosphere at 13,000 mph and enduring temperatures of up to 3,800 degrees Fahrenheit, a peak deceleration of up to 15 Gs, and the jerk of a supersonic braking parachute–that’s just the opening act.
For NASA’s Mars Science Laboratory, the real fun will start 50 seconds before touchdown when the one-ton nuclear-powered rover falls free of its parachute for a nail-biting rocket-powered final descent to the surface. (For the main story in this package, see “On Mars, satisfaction awaits Curiosity.”)
Unlike past Mars missions, the Curiosity rover will not set down atop a legged lander or bounce to the surface surrounded by shock-absorbing airbags. Instead, it will be lowered to the ground and set on its wheels by a slowly descending “sky crane” designed to unreel the lander like a lure on a fishing line.