Did life ever exist on Mars? That is a question that scientists, and the rest of us, want to know. Now, thanks to NASA’s Mars rover Curiosity, a possible answer to this question could be “yes.” Not only do we now know that phosphates, a basic component of DNA, could have existed on the red planet, but Curiosity also discovered water on the planet, something that is believed necessary for life to form. After carefully studying a large crater on the planet’s surface, scientists believe a freshwater lake existed there that could potentially have contained microbial life.
So how do scientists know that this crater, known as Gale Crater, was once a lake? They studied samples taken by Curiosity of its sedimentary rock. By looking at that rock’s chemistry (it contained elements like oxygen, carbon, hydrogen and sulfur), they determined that this particular area of Mars likely contained a freshwater lake around 3.6 billion years ago. Scientists believe that the calm lake was present on Mars for up to hundreds of thousands of years. Because of the rocks’ composition, scientists think that this lake could have possibly sustained a type of microbial life called chemolithoautotrophs, which are often found in similar conditions on Earth.
Of course, this doesn't mean that we’re at all sure that Mars once contained life, and we have to point out that finding ideal conditions for life is not at all the same as finding evidence of life itself. However, as of now, this is the closest we've come, and it gives us a reason to continue exploring its surface. So that makes this discovery a pretty big deal.