[X] My Assistant

[imran]

Wreckage of Beagle found scattered in Mars crater

Talk about being unlucky assuming this is confirmed.

[Guest_BruceMoomaw_*]

Given how close MER-A (I refuse to use that cornball name "Spirit") came to disaster because of the unexpectedly low density of Mars' upper atmosphere -- even after its hasty last-minute reprogramming to open its parachute earlier, it came within 3 seconds of opening the chute too late to avoid a crash -- I think this has an excellent chance of being the fatal flaw in Beagle: it just came down too damned fast due to the lower than predicted Martian air density, and kaplooey. We'll never know whether some additional flaw also existed that would have done it in anyway, given the flaws that the failure board found to be riddling its design -- but the air density problem by itself would have been enough, and is very likely to have happened.

I am only now coming to realize how hard it actually is to land on Mars because of its peculiar halfway nature. As Ed Strick (and Rob Manning) say, it's very hard to utilize either purely aerodynamic braking or purely rocket braking to land on it, and Mars' thin air density has a height profile such that it's difficult even to combine the two effectively enough to get the braking job done in time. We may actually have been very lucky up to now to pull off as many successful Mars landings as we have -- most of the previous failures (Mars 2, 3 and 7; Polar Lander) were due to unconnected technical problems, but Mars' atmosphere alone may seriously endanger landers, and may conceivably have done in both Mars 6 and Beagle as well as almost killing MER-A. And the bigger the lander, the more serious the problem rapidly becomes.

[The Messenger]

I am only now coming to realize how hard it actually is to land on Mars because of its peculiar halfway nature.  As Ed Strick (and Rob Manning) say, it's very hard to utilize either purely aerodynamic braking or purely rocket braking to land on it, and Mars' thin air density has a height profile such that it's difficult even to combine the two effectively enough to get the braking job done in time.  We may actually have been very lucky up to now to pull off as many successful Mars landings as we have -- most of the previous failures (Mars 2, 3 and 7; Polar Lander) were due to unconnected technical problems, but Mars' atmosphere alone may seriously endanger landers, and may conceivably have done in both Mars 6 and Beagle as well as almost killing MER-A.  And the bigger the lander, the more serious the problem rapidly becomes.

Both of the Viking craft used more of their fuel than expected (8-15%), but still held excess in reserve. Every single Martian landing craft has enter at a higher attitude and come down harder than expected, deployed parachutes later than expected, and left unanswered questions about their parachute drag coefficients and descent profiles. Every one. With lower engineering margins, the Mars 2,3,6, Polar lander and Beagle did not have chance.

The MRO has the potential of providing a definitive answer to these curiousites, but you must be willing to look at the possibility that there are very weak, second order gravitational effects. Weak second order effects, based upon the total mass of a system cannot be ruled out from our earth-moon platform, because the local mass-fraction is dominated by the solar mass. But further from the Sun and orbiting at an altitude of only 150 km, the MRO will sense gravity anomalies that are a full and unexplicable order of magnitude greater than the 300km orbiters.