A fascinating new NASA report explores how we might search for life on Jupiter’s moon Europa by sending a lander there.

Europa has long been of interest, as it’s believed to have a vast saltwater ocean beneath its icy surface, containing more water than there is on Earth – and possibly having the necessary conditions for life to exist.

With this in mind, NASA is planning to send a mission to Europa in the early 2020s called the Europa Multiple Flyby Mission (EMFM), which would perform 45 flybys of the moon and study it in detail from space.

But the dream has always been to actually send a lander to the surface to directly sample the moon. Last year, Congress gave NASA the funds to investigate how they would go about doing that, and NASA put together a team of 21 scientists in June 2016 to work it out.

Now, they’ve returned a report on a Europa Lander, separate to the EMFM. The in-depth report makes for fascinating reading, and we’d recommend checking it out, but we’ll run through some of the key points here.

“Europa may hold the clues to one of NASA’s long standing goals – to determine whether or not we are alone in the universe,” the report notes. “The highest-level science goal of the mission […] is to search for evidence of life on Europa.”

To do this, the lander would launch in 2024 or 2025 on NASA’s upcoming Space Launch System (SLS) rocket, with a Carrier Relay Orbiter (CRO) traveling with it to orbit above the surface and transmit data back to Earth. Owing to the intense radiation around Jupiter, the lander and orbiter would be designed to last only about 30 days.

Once on the surface, lowered there by a powered "sky crane" similar to how Curiosity landed on Mars, a suite of instruments would allow the spacecraft to study Europa and search for life. It would collect five samples from up to 10 centimeters (4 inches) below the surface using a robotic arm, analyzing them on board.

^{Scientists are pretty sure Europa has a vast ocean under its surface. NASA}

A key problem, though, is that we have no way of directly detecting life on another world. There just simply isn’t an instrument that exists that can tell you definitively if life is there or not. So instead, the lander would put together nine lines of evidence for biosignatures.

One of these would be the Microscope for Life Detection (MLD) instrument, which could find microbial cells as small as 0.2 microns in diameter, roughly the size of small bacteria on Earth. Other instruments would look for cell-like structures and work out if samples came from the ocean.

A seismic instrument, meanwhile, would measure the thickness of Europa’s ice shell and the thickness of its ocean, through “acoustic monitoring of cracking events in the ice shell.”

To keep the instruments safe from Jupiter’s radiation, weighing a total of 42.5 kilograms (93.7 pounds), they would be kept inside a vault. The only instrument not in the vault would be the Context Remote Sensing Instrument (CRSI), which would take images on the surface.

Of course, the detection of life is not a guarantee, but the scientific return of the mission would still be vast. Not least, it would tell us if Europa is a potentially habitable world, and lay the groundwork for a possible future robotic mission to explore beneath the icy surface.

“This mission would significantly advance our understanding of Europa as an ocean world, even in the absence of any definitive signs of life, and would provide the foundation for the future robotic exploration of Europa,” the report says.

“These measurements would then feed forward into designs of future robotic vehicles that would explore across the surface, or down into the subsurface.”

This would be the first direct search for life on another world since the Viking landers touched down on Mars in the 1970s. There’s no guarantee it would go ahead yet; this is merely a look at how feasible such a mission would be. NASA said it would now be “engaging the broader science community to open a discussion about [the report’s] findings.”

But there’s little doubt there is huge interest in sending a lander to Europa. In our search for life beyond Earth, this icy moon of Jupiter might be one of our best bets.