On Wednesday September 19, the European Space Agency (ESA) spacecraft Schiaparelli—named after Giovanni Schiaparelli, an astronomer who described many features on the surface of Mars—attempted to land on the aforementioned planet. The probe was using a new type of landing system that involved a heat shield, parachutes, retrorockets, and a crumple zone. Unfortunately, ground control lost contact with the spacecraft during the descent. A brief analysis of the data that the lander was continuously streaming back to its parent ship, the Trace Gas Orbiter, suggests that it hit the ground at high speed after unexpectedly free-falling from a few kilometers up.
Schiaparelli
Schiaparelli was a small space probe that was designed (primarily) to test the landing system that will be used by a 2021 ESA rover to land on the planet. The landing system is complicated; first, the probe entered the Martian atmosphere at 5.8 km/s. At that high speed, the probe compressed the air in front of it so much that it heated up, necessitating a heavy heat shield to protect the delicate lander. This is the same effect that produces flame-effects when craft re-enter Earth’s atmosphere, and not friction as is frequently thought.
After losing most of its 21 000 km/hr initial speed to air drag, Schiaparelli deployed parachutes to slow down further. Both the heat shield and the parachute deployment went off without issue. Following standard procedure, the probe would detach from the parachute shortly before landing, at which point retro-rockets would fire to bring the probe to a not-quite hover at 2 m above the ground. The rockets would cut out and the probe would fall to the ground, cushioned by a crumple device. A Doppler radar altimeter, which measures the altitude of the spacecraft during decent, would be used to provide feedback to the probe and coordinate the different stages.
Unfortunately, standard procedure was not followed; the parachute released far too early, and then the retro rockets fired for four seconds, not thirty seconds as expected. It is currently believed that the probe free-fell from a kilometer or two, hitting the ground at a tremendous speed that the crumple zone could not protect against.
Even though Schiaparelli was designed to be a trial run of the landing system, the crash is disappointing. The probe would have survived for only two to eight Martian days (or Sols), collecting previously-uncollected data about airborne dust. While it is better that the small lander was destroyed than the more ambitious 2021 rover that is to follow, it would have been nice if the landing had gone off without a hitch, leaving the team confident in their system.
This landing is also disappointing because it is the second time that the ESA has attempted to and failed to successfully deploy a probe to Mar’s surface; the 2003 Mars Express orbiter came with a simple small probe named “Beagle 2.” That probe never made contact with Earth after entering the Martian atmosphere. However, the probe was finally located in January 2015 using satellite images, its communications array hidden behind undeployed solar panels. This has at least allowed the ESA to boast that they have successfully joined the small elite club of organizations that have put a payload on Mars.
The Trace Gas Orbiter
The Trace Gas Orbiter (TGO) is the orbiter that Schiaparelli accompanied to Mars. It detached from the probe on October 16, after which the two crafts entered different orbits. While Schiaparelli zoomed towards the surface of Mars, the TGO has entered a higher orbit. It will spend a few months dipping down into the atmosphere to slow down in a process known as “aerobraking.” This does two things to the orbit: it slows the spacecraft down, making the orbit smaller, and “circularizes the orbit,” making it less ellipsoidal. Once aerobraking brings the TGO into a circular 400 km orbit in late 2017, it will begin to perform its science activities.
Among the scientific activities that the TGO will be performing is looking for traces of methane. Methane has been identified by several craft on and around Mars, and it is possible that the gas is coming from a microbial source. However, it is also possible that the methane is coming from some geochemical process like a volcano. The TGO will look for the presence of both methane and other chemicals in order ascertain the more likely source; methane coinciding with other hydrocarbons like ethane and propane suggests biological activity, while it coinciding with sulphur dioxide indicates geological processes are at work.
It will be a while until the TGO gets down to science, revealing exciting new things about the Martian atmosphere. Unfortunately, with the presumed loss of Schiaparelli, there won’t be much news out of these spacecraft until then, except the ESA hopefully diagnosing what went wrong with the probe’s landing.
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