Slashdot Mirror
Mars Phoenix Probe Successfully Launched
necro81 writes "The Mars Phoenix lander, built from the ashes of two earlier Mars missions, successfully launched atop a Delta II rocket from Canaveral this morning. The mission takes the 350-kg lander to northern latitudes (comparable to Greenland or Siberia) to investigate subsurface ice for the chemical precursors of life. The lander should arrive on Mars on May 25, 2008. 'NASA has never attempted to land a spacecraft on Mars at such a high northern latitude. A lander intended for the red planet's South Pole went silent immediately upon arrival in 1999. That failure, combined with the loss of the companion Mars orbiter, prompted NASA to cancel a 2001 lander mission. The parts from that scrapped mission were used for Phoenix, thus its name, which alludes to the mythological bird that rises from its own ashes.'"
The absence of a magnetic field on mars has some interesting consequences. Since Mars and Earth were formed from the same material, it is very surprising that Mars doesn't have oceans. One of the theories is that the solar wind of particles from the sun carried away the atmosphere, and so the oceans just evaporated away until it became so cold the remaining water froze into the polar ice caps. Recent estimates indicate that Mars loses some 100 tons of atmosphere every day. The Earth is protected from the solar wind by its magnetosphere, which results from the magnetic field. Mars's magnetic field, on the other hand, disappeared some 4 Billion years ago when the planet's core cooled off.
If Mars has no magnetic field what determines North?
This animation from Maas Digital shows that the planned landing of Phoenix is very ambitious. As the spacecraft enters the Martian atmosphere it is protected by a heat shield. Notice the ice cap on the northern pole, which was constructed from images from the Mars Global Surveyor. A parachute will be used to slow the descent, but because the atmosphere is so thin, it will still be going *very* fast. You can see clouds in the background, which were also seen from orbit by MGS.
A key event happens after the parachute and heat shield rip away: the landing gear deploys, and then the retro-rockets kick in. One problem with the ill-fated Mars Polar Lander was that the sequence of the last two events was reversed. An on-board sensor felt a jolt as when the landing gear locked in and assumed that the landing had taken place. The engines were shut off and the spacecraft plummeted to ground. So close...
It is very difficult to test landing procedures here on Earth. The gravity on Mars is only a third of what we have, and a simulation is never as good as testing in realistic conditions.
The summary mentions that the name is derived from the mythical phoenix, but this is only part of the story. The probe - the first to be launched as part of NASA's low cost "scout" program - was led by the University of Arizona. It's safe to guess that Phoenix also refers to the capital of the arid state. I wonder if I'm the only one who keeps confusing the leadership of this mission with the ubiquitous University of Phoenix.
For this and more information on the Phoenix mission, see the mission page.