How does NASA plan to keep samples from Mars free of contamination (and contamination of Earth)?

NASA’s Mars sample return mission is getting closer and closer. The overall mission architecture just reached a new milestone when Perseverance assembled the first sample to be sent back. But what happens once that sample gets here? NASA and its partner, ESA, are still working on this, but they recently published a fact sheet that describes what will happen in the first step of the process – the return to earth.

This return will take place in the middle of the desert in the western United States, in an area called the Utah Test and Training Range (UTTR). While this may seem like an odd place to carry out such an important mission, there are a few things going for it.

First, it’s in the continental US, which gives it relatively easy access to state-of-the-art laboratory equipment available across the country. NASA is the most likely candidate to muster all the resources needed to quarantine the sample to keep it separate from the wider Earth environment, which would help eliminate the (admittedly unlikely) event of a Martian superbug breaking loose.

Reliable containment is one of the reasons the agency refuses to waterboard. This would reduce the impact on the sample, but there would also be a small chance that the capsule could sink in the ocean, and the small pieces of Mars inside could be lost to the sea. It would be nice to avoid that, so it’s better to land on land.

But this land needs to be insulated, another advantage of UTTR. Not only is it not close to roads, but it is already a restricted airspace, as it is the site of many missile and aircraft tests. Being isolated also means that the capsule is less likely to affect something important if something goes wrong with the trajectory.

This will be especially important given the landing method chosen for the MSR capsule. It will fall to the ground using only air braking – no parachute required. Therefore, it will go much faster than the return of a normal capsule with a parachute. But according to NASA’s calculations, the samples and their containers should withstand the impact. Not using a parachute significantly simplify the design of the capsule and reduce its weight, both of which are significant factors, given that the capsule itself must return from Mars.

Even so, the impact itself will make a nice dent in the landscape. NASA has already begun testing using a mock-up of the MSR sample return capsule. This created a series of 1.3 meter wide craters in the landscape and ejected material 15 meters from the crater.

Based on samples and capsule survive, the next step is to transport them safely to a laboratory where they can be properly studied. That, after all, is the whole purpose of the Mars Sample Return mission. That part of the program has yet to be determined, but knowing that the samples will be in the middle of the Utah desert is at least a place to start.