Around the start of the next decade, a piece of another world will be brought to Earth, studied, experimented upon, gawked at and, it’s hoped, found to contain life.

No, not the moon. Luna is dead, always has been. But Mars may have once been alive ? may still be.

Signs of potential life have been accumulating for years, through satellite flybys and the trundling progress of various rovers, which have been a presence on the red planet since 1997.

The first of these were sent by NASA, and it appeared the U.S. space agency would be the first to bring anything back from Mars, collecting material carefully prepared by Perseverance, the latest and most advanced of all the robot Martians.

But that mission was delayed multiple times and finally scrapped this January, clearing the decks for history to be made by a newer space power: China.

“If there is any evidence of life on Mars, that would completely rewrite the history of life as we know it,” said Yiliang Li, a professor at Hong Kong University’s Department of Earth and Planetary Sciences and a member of the Tianwen-3 Mars sample-return mission.

If all goes to plan, Tianwen-3 will launch in two stages in 2028, dispatching a lander to gather samples on the Martian surface along with an ascent vehicle that can take it up to another craft waiting in orbit, which will fly the samples back to Earth, arriving in 2031.

Prof. Li and his team are currently poring over satellite imagery of Mars to narrow down a list of potential landing sites to three by the end of this year ? a primary site and two fallback options, in case of dust storms or other complications.

Selecting such a site is a delicate dance between the scientific and engineering sides of the mission, Prof. Li said. His team wants to prioritize parts of Mars with potential signs of water, seen as the best chance of finding biosignatures ? evidence of past or present life ? and his colleagues want to make sure the lander doesn’t crash or get stuck, wasting years of effort and billions of dollars.

“The problem is where geologists want to go is not where engineers want to go,” said Sanjeev Gupta, a professor of earth sciences at Imperial College London who has worked on multiple NASA missions to Mars.

With the advance of telescopic technology in the 19th and 20th centuries, some believed they saw signs of activity on Mars, with American astronomer Percival Lowell confidently declaring in 1907 that “the planet is at present the abode of intelligent, constructive life.”

Closer examination showed such observations ? including a network of canals ? to be a mirage, and by the time NASA and the Soviet Union sent probes to Mars in the 1960s and seventies, it was generally accepted to be a dead planet.

But that conclusion has been challenged in recent years, thanks both to discoveries on the planet itself ? including evidence of water in far greater quantities than previously thought ? and on Earth, where extremophiles have been found thriving in conditions presumed hostile to life.

“The Tibetan Plateau has brines with very high salinity and a very low freezing point,” Prof. Li said. “There could be similar very salty water circulating vertically from the depths to the surface of Mars, with temperatures and nutrients that would be suitable for extremophiles on Earth.”

Rovers have already found potential biosignatures on Mars, but proving they were left by living organisms rather than chemical reactions, let alone demonstrating that life as we know it exists, is likely beyond what even the most advanced robot can do on the surface.

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“We need to analyze chemical signatures of life in Earth laboratories,” Prof. Gupta said. “Even if we find evidence for life, it won’t be a slam dunk – any initial tentative discovery will be disputed by the scientific community ? but it will be the engine of research, the engine of discovery.”

Perseverance’s payload will remain planet-bound, however, after the sample-return project fell afoul of sweeping cuts to NASA’s budget under President Donald Trump.

The Perseverance team will now become bystanders to the Chinese mission, which, while less ambitious – targeting one area and source of samples, rather than collecting them over years at various locations, as Perseverance has done – does appear to be going ahead, with Beijing firmly in support of the Tianwen program, alongside its own plan to send a crew to the moon.

That program ? Chang’e, named for a Chinese moon goddess – has already had great success, landing the first rover on the far side of the moon and retrieving samples from the surface.

Getting a sample off Mars is a vastly more complex operation, however. The average distance between Earth and Mars is more than 500 times the gap between us and the moon. The Artemis II flyby took a total of nine days; just reaching Mars takes seven to 10 months.

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Unlike the moon, Mars has an atmosphere, making landing far more difficult and taking off even more so. Any sample then has to dock with the orbiter, return to Earth and land safely, after which it will be quarantined, both to avoid contaminating any potential biosignatures and for the far less likely chance of infecting our biosphere with some kind of Martian life.

Given the more limited samples that will be collected by Tianwen-3, Prof. Gupta said it was “highly unlikely” they will contain life or evidence of past life, but they will still provide a huge amount of information about the geology of Mars, as well as serving as a proof of concept for future sample-return missions.

Returning samples from Mars would enable us not only to understand that planet better but our own. Unlike Earth, Mars does not have plate tectonics, which means that apart from the effects of ancient seas and the occasional asteroid impact, the surface has been largely static since its creation, so studying it could give us an idea of what Earth was like in its earliest stages.

“In some ways, going to Mars is learning about ourselves,” Prof. Gupta said.

While a great deal of focus is on searching for life on Mars, proving the opposite could give us insight into how and why life exists on Earth. As the existence of extremophiles demonstrates, life fills every niche, but this makes finding the point in the fossil record where life began exceptionally difficult.

“Let’s say no life arose on Mars. That means we can get prebiotic chemistry, which we don’t have on Earth,” Prof. Gupta said. “There are tentative things in [Earth] rocks that are hugely debated, around the 3.9-billion-year mark, but we don’t have a prebiotic rock record, and Mars could give us that.”

Prof. Li said he was disheartened by the increasing focus – from figures such as Elon Musk but also governments – on sending humans to Mars when we still barely understand the planet.

“Mars has very high radiation, it’s very cold, very dry, but there are still extremophiles that could surface in those conditions,” he said. “If we bring people to Mars, we could contaminate the entire planet. We should be very careful.”