RISING FROM THE PHOENIX
InSight owes a big debt of gratitude to a previous lander that NASA put down on the Martian surface
To those who follow Martian missions, InSight might look rather familiar. That’s no surprise: it is closely based on the Phoenix lander, which touched down in Mars’s polar region on 25 May 2008. The InSight team has borrowed the design for the lander’s descent hardware, base structure and robotic arm from Phoenix, but added a completely new set of science instruments.
This helped to reduce costs dramatically but also put several limits on the mission. Phoenix only operated for six months, but InSight is designed to last for at least a Martian year, if not longer. This means it has to land on the equator, or the solar panels won’t be able to collect enough power during the dim winter months. In addition, the descent systems will only work over a certain range of altitudes and the only place on the equator at the right elevation is the flat Elysium Planitia region.
The Phoenix mission itself was concerned with the surface, rather than what lay beneath, and attempted to find out how hospitable the Martian soil was to life, past or present. The robotic arm took soil samples that were then heated, revealing they contained water ice, and the chances of habitability initially looked bright.
The excitement was short-lived as Phoenix also found perchlorates, a chemical that reduces the freezing point of water. While this could mean it is possible for liquid water to exist on the surface, when combined with other minerals and subjected to Martian levels of ultraviolet radiation, perchlorates cause a 10-fold increase in cell death. If any life did evolve on Mars, it would have found itself in a very hostile environment.