Telescope Reviews: PHOENIX Landing Coverage

Because the design of the lander used hardware from a previous canceled mission that was never intended to move (just land in one spot). At the time when the new Scout-class missions were developed ("Better, faster, cheaper"), several options were considered for landing spacecraft on Mars. The ones that had worked previously were the Viking 1 and 2 landers, so naturally, two of the landers (Mars Polar Lander and Mars Surveyor Lander) were to use that already established landing technique (parachute, followed by a final descent using landing thrusters and three landing legs for support). Like the Vikings, the two landers were never intended to move but just give us more information about single sites, since rovers had not been in the cards at that point. The "wild card" at the time was the sort of "engineering" demonstration project using air bags, named "Pathfinder". It carried a small short-range experimental remote-controlled rover (Sojourner) as a sort of "bonus", but overall, the project was more an engineering test to see if this new landing technique actually would work. Thus, the science payload was kept to a modest amount, and the project was also given a go to try. Of course, no one knew whether the air bag system would work for a Martian landing, so the already established parachute/descent thruster method would be used for other two landers in case the airbags didn't work. Well, they did and the Mars Polar Lander didn't, although that was not necessarily because there was anything wrong with the landing method. However, the 2nd lander (Mars Surveyor) was canceled after the dual failures of Mars Polar Lander and Mars Climate Explorer, so the hardware for the Mars Surveyor Lander hardware sat unused until a proposal was made to put a new science payload on the lander portion and send it to the northern polar region. This could be done for a cost that was less than that of a new dedicated polar landing probe, and thus, the Mars Phoenix mission was born. Putting wheels and motors on the lander would have added weight, complexity, cost, and design time to the mission, so it was decided to just use the existing hardware and put up with the more limited reach to get back to Mars soon and save some money in the process. Someday, we will probably have some rovers land in the polar regions, but for now, we should get good science from our little "one shot" foray into the Martian arctic landscape. Clear skies to you.