NASA has just two Mars Sample Return mission lander options left

NASA says it needs until 2026 before making a final decision on how the Mars Sample Return (MSR) mission will work.

During a briefing on January 7, the US space agency confirmed it had whittled down the options to two: The Jet Propulsion Laboratory (JPL), which would employ the sky crane technology - used to land the Curiosity and Perseverance rovers on Mars - to deposit a lander on the surface of the red planet; the other would use a commercial vendor to get the lander to Mars.

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The lander itself would feature a small rocket, the Mars Ascent Vehicle (MAV), which would take the samples to a spacecraft provided by the European Space Agency (ESA) for a trip back to Earth.

The plan relies on the Perseverance trundlebot being able to make it to the lander, and a spare arm developed as part of the Perseverance mission and fitted to the lander taking the samples from the rover and loading them into the MAV.

The price given for the JPL option was between $6.6 billion and $7.7 billion, while the commercial providers came in between $5.8 billion and $7.1 billion. NASA did not go into detail on what the commercial vendors suggested, citing proprietary information, but did note that as well as heavy landers, an architecture along the lines of JPL's sky crane had also been proposed.

NASA noted that it would not be a straightforward reuse of the sky crane technology – the system would need to be 20 percent bigger than the one used to land the rovers.

Some decisions have, however, been made. The lander won't include solar panels but will instead use a radioisotope thermal generator (RTG) for power, meaning it would be better able to handle dust storms and keep the solid rocket motors on the MAV warm.

The estimated budget for the Mars Sample Return mission ballooned to $11 billion during 2024, and that, coupled with a return date of 2040 for samples from Mars, resulted in a call to find an alternative approach with a price tag in the range of $5 billion to $7 billion.

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The revised plan ditches the idea of an Ingenuity-type helicopter to retrieve the samples – Perseverance will have to make it to the lander – and brings forward the return date to as soon as 2035. However, that might slip to 2039 if funding doesn't materialize in a timely manner.

Either date will still put the US behind China, which is planning its own Mars sample return expedition in the form of Tianwen-3, due to launch in 2028. NASA administrator Bill Nelson was dismissive of the Chinese approach and described it as a "grab and go kind of mission" compared to the methodical approach taken by the Perseverance team, where samples were taken from a variety of locations.

Nelson might be correct from a scientific point of view, but the optics of the US not being the first to retrieve a Mars sample might not play well with the incoming US administration, who will need to sign off on the approach. ®