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The Planetary Society Weblog

By Emily Lakdawalla

Phoenix landing site woes

Jan. 17, 2007 | 11:46 PST | 19:46 UTC

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Aviation Now and The Rocky Mountain News have reported on two problems facing the Phoenix Mars lander, which is supposed to launch this summer: a $10 to $35 million cost overrun (which, though not at all trivial, does have an easy enough fix, though the future consequences to other Mars missions may be tough to stomach) and a serious hazard within the planned landing region (which is harder to fix).

Among Mars Reconnaissance Orbiter's highest priorities for the first months of its primary science mission is imaging the proposed Phoenix landing sites. The landing site selection process has been in progress for years, and years of work have resulted in the downselection to three spots within an area of Mars' northern plains, a box that spans from 67 to 70 degrees north latitude and 126 to 135 degrees east longitude. Mars' northern plains seem utterly featureless, so this seemed a safe enough place to land. But here's what it looks like to HiRISE's sharp eyes:

HiRISE image of the northern Martian plains: 50 centimeters per pixel
Credit: NASA / JPL / U. Arizona

(I wrote more on this particular image when it was released two months ago.) The whole place is covered with boulders of various sizes, many of them quite as big as Phoenix itself. Needless to say, landing the spacecraft on top of one of these things would very likely doom the mission. So now the team is apparently scrambling to find a safe site.

I was a little concerned that Mars Reconnaissance Orbiter might have focused its early imaging efforts in support of the Phoenix mission on that one small latitude and longitude box, but I did a quick survey of all of the images released to date on the HiRISE website and found 50 of them labeled "Northern Plains," only a dozen or so of which cross into that box. They all seem to contain those pesky boulders. Many, but not all, of the other Northern Plains images also seem to contain those pesky boulders.

I'm sure that the Phoenix team's first instinct was to wish that they'd remained in their state of blissful, pre-MRO ignorance of the hazardous nature of their selected landing site. But, though this may be bad news, it may well have saved the mission, and the HiRISE imaging campaign will hopefully lead quickly to the selection of a safer site. The Phoenix team has a previously scheduled landing site selection meeting Monday and Tuesday next week, and they have a lot of work to do.

Click to enlarge >

Phoenix
This artist rendition of the Phoenix Lander shows the firing thrusters just before the lander touches down on the martian surface. Credit: NASA/ JPL / art by Corby Waste