Curiosity has found new hints of the Red Planet’s past — and they look intriguing.

So far, we’ve only ever found life on Earth. Until very recently, we didn’t even know of other Earth-like planets — but that all changed, fast. We’ve since found thousands of exoplanets, some of which are very promising in terms of habitability.

But for now, at least, we can only explore the planets inside our own solar system. Mars was always a candidate for extraterrestrial life. It’s comparable in size to our planet, lies at a good distance for the Sun, and it seemed to have a decent atmosphere at some point. More recent investigations have found strong evidence for ancient systems of water. Other exotic places, like Europa or Enceladus may also harbor (or have harbored) life, but Mars will always be a promising candidate.

Very promising, as recent evidence shows.

Curiosity has drilled two small cores into what researchers believe to be lake sediments. Using the scientific instruments at its disposal, the rover analyzed the sediments, tracing their chemical makeup.

This makeup suggests that, in addition to Mars’ wet past, we can also infer that the lakes (or seas) may have been very rich in minerals, and were also salty.

In other words, Mars’ oceans bared striking similarities to those on Earth.

It gets even better. Not only was the chemical make-up similar to that of Earth, but the acidity (pH) was also close to that of Earth’s modern oceans.

We know that life can emerge in Earth’s oceans, so if water on Mars looked a lot like that on our planet, there’s a good chance life might have emerged there as well.

However, this would have been the case billions of years ago. Nowadays, Mars is a pretty barren wasteland, and it’s not clear if any life can exist there at all — even microbial life.

But even if life on Mars doesn’t exist now, it might have been there at some point in the past, which begs the question: how likely are we to find traces of it, such as fossils or more likely, chemical traces of living creatures?

That’s not exactly clear, and it’s not something that Curiosity is well-equipped to do.

NASA’s 2020 rover, on the other hand, will do just that: look for signs of life (especially microbial life) and habitable conditions on Mars — and we can’t wait for the results.

The study has been published in Nature Communications.