Earlier this month, the European Space Agency lost contact with the lander stage of its ExoMars mission. The lander, Schiaparelli, separated from the ExoMars Trace Gas Orbiter on October 16, and began its descent on October 19. The ESA lost contact with Schiaparelli roughly one minute before touchdown. But there were signs of an issue before that point. While the lander’s parachute deployed flawlessly, it ejected its back heat shield and parachute earlier than was it was supposed to. The lander’s thrusters were meant to fire for 30 seconds, but telemetry indicates they only fired for three seconds.
NASA was able to provide images of the landing site almost immediately, but the first shots weren’t taken with the high-resolution Hi-RISE camera on the Mars Reconnaissance Orbiter. Now we have that information, and it sheds some light on Schiaparelli’s last moments, while raising questions at the same time.
Here’s the high-level shot of the entire area. Several areas of interest have been highlighted:
First, at the bottom of the image, there’s a large white spot and a smaller, slightly darker spot below it. These are thought to correspond to the rear heatshield and parachute that protected and slowed the lander during the first stage of the process. Schiaparelli was intended partly as a test for the ESA’s landing system, so it’s important to know which parts of the system functioned properly and which did not. The parachute deployed properly, but was jettisoned too early.
The large spot in the center-left portion of the image is thought to be associated with Schiaparelli itself. The ESA describes it as follows:
The arcing dark mark is hard to interpret, as this type of feature is normally only created by a meteor approaching at extremely high velocity with a low incoming angle. The rover was moving much too slowly and directly on-target to create this type of arc; the ESA theorizes that the hydrazine tanks on the module might have preferentially exploded in a single direction. The front heatshield that was ejected earlier in the descent process can be seen in the top-right of the image.
Right now, all data points to a software problem with Schiaparelli, rather than a hardware malfunction. The spacecraft appears to have become confused about its own location, given that it jettisoned its own parachute so quickly, fired its landing rockets for just seconds, and then turned on some of its scientific instruments for monitoring ground conditions. This all suggests that the spacecraft thought it was much closer to the ground than it was — if the altimeter thought the craft was just meters from the surface, it would explain why it fired its rockets for just three seconds.
For now, Schiaparelli’s hardware all appears to have been in perfect working order when communication from the craft ceased. The ESA team will be analyzing its telemetry data, reviewing the rover’s software, and simulating the approach in software to try and determine what went wrong. NASA may also be able to provide full-color images or additional details from orbit that help crack the case. The follow-up ExoMars mission is meant to launch by 2020, so solving this problem and ensuring it doesn’t happen again are top priorities.