A look at space exploration, the search for life beyond Earth, extreme life forms, and the daily musings of a graduate student in London.
ExoMars may be more than 5 years away from Mars, but another mission will be landing in less than 3 weeks! The Phoenix Mars Lander is NASA’s latest attempt to “follow the water”, targeting the northern plains of Mars in search of H2O. In 2001, the Mars Odyssey spacecraft detected hydrogen (which is interpreted as water…what else would it be?), and it’s concentrated at high latitudes. Here’s a color-coordinated water map: red means little, blue means lots.
The quest for life (or signs of past life) has become a quest for water (or signs of past water), and this has led to the northern plains. The initial discovery was essentially an electrical signal, and no one really knows what this means physically. It seems pretty clear that it’s not liquid, but there’s still plenty of uncertainty. Is it pure ice relatively deep beneath the surface? Or might it be an ice-soil mixture a little closer to the surface? This is more than an academic question because Phoenix is fitted with a scoop that will dig a trench up to 1m deep—if the ice layer is beneath this depth, the mission will become a lot less interesting.
Needless to say, everything has been optimized to make sure the chances of finding water ice are as high as possible, but you never know. And unlike the rovers, Phoenix has no movement capabilities, so if the landing site isn’t perfect, you’re pretty much out of luck.
I’m also a little uneasy about the landing strategy. Airbag landing on Mars, once deemed too radical, has gone three-for-three, while retro-rockets seem a little less stable. Phoenix is equipped with retro-rockets less for landing safety reasons and more for “capability development” purposes. It boils down to this: when humans go to Mars, they might not be too excited about an airbag landing, so we need to practice setting payloads down gently on the surface. It’s just a little frightening when you’re practicing with a $420 million piece of machinery.
And so, the drama builds. Finding actual water molecules on Mars would be a first, and a meter-deep trench would be the most impressive construction project to date on the Red Planet. I was fortunate enough to work on the team that selected the landing site for Phoenix, so it will be a particularly gut-wrenching few weeks! Hold on to your hats!
Last updated: Sunday, 04 May 2008 - 23:32 GMT
© 2008 Nature Publishing Group
I’m also looking forward to this landing. Who’d have thought the Mars rovers would still be working when Phoenix landed?
I agree that the retrorocket landing seems more risky. But didn’t the Viking probes both achieve this over 30 years ago, presumably with much less sophisticated control computers?
Indeed, the Viking landers did successfully implement retrorockets…but several other similarly-equipped probes have been less fortunate. A brief history of failures, from what I can gather:
Mars 2 probe. Soviet lander that crashed, likely due to improper trajectory, not retrorocket issues.
Mars 3 probe. Soviet lander that successfully touched down, only to mysteriously stop transmissions after a whopping 14.5 seconds of operation.
Mars 6 probe. Soviet probe that landed at 61 meters per second – indicating some sort of retrorocket failure.
Mars 7 probe. Yet another Soviet mission that crash landed due to either an altitude control or retrorocket problem.
Mars Polar Lander. NASA mission that likely crashed after a free-fall from 40 meters. The retrorocket system seems to have interpreted some vibrations as a successful landing, resulting in a premature shutdown.
So I suppose much of the bad reputation of retrorockets can be blamed on the Soviets, but still – not a great track record. And in fairness, one airbag mission has failed – the Beagle 2.