So, yes, we are a bunch of Curiosity fanboys and girls here at SciShow, we make no secret of that. If Curiosity went on tour we'd be in the front row throwing our undergarments at it. And why not? It's a nuclear-powered mobile laboratory on the surface of another planet the size of a small car - Harry Styles ain't got nothing on that.

And just in time for the holiday season Curiosity has just gifted the world another sleigh-load of space data. There is now mounting evidence that ancient Mars was pretty darn habitable over larger areas and longer periods of time than we ever thought. Stick around to learn why.

I'm Hank Green, and welcome to this special breaking edition of SciShow News.

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The Curiosity Rover, aka the Mars Science Laboratory, landed on Mars in August of 2012. Part of its mission is to find evidence of past life and since then we've been giving you updates about its findings.

Now it's been a few months, but researchers working with Curiosity presented a truckload of data today at the American Geophysical Union's Fall Meeting in San Francisco, California.

When we last checked with Curiosity it steered off its planned course towards Mount Sharp to investigate some curious looking formations, including what looked like an alluvial fan, a deposit that forms lake inlets, and a 5 meter deep trench called Yellowknife Bay. When it arrived at the deposit, Curiosity captured images of what appeared to be layers of fine-grained sedimentary rock. Mission scientists explained today that this kind of rock forms out of sediments that had settled to the bottom of a body of water. So Curiosity drilled through the bottom layer, deemed Sheepbed, and with its Chemin instrument used X-rays to determine the formations' basic chemical make-up. Sure enough: it's mudstone, a sedimentary rock that forms in water.

Now Curiosity's previous sample, Rocknest, was also mudstone. What's new here is that everything we've learned so far indicates that Gale Crater, the massive crater that Curiosity has been roving since it landed a year and a half ago, was itself actually an ancient lake. Not only that, Gale Crater was a very habitable lake.

Chemin determined that the two samples taken from Sheepbed, known as John Klein and Cumberland, are rich in carbon, hydrogen, oxygen, and sulfur, all elements that are key ingredients to life and that can be used as energy sources for that life. And while Curiosity didn't detect phosphorus or nitrogen, to have the most important elements for life, it did detect compounds that form in the presence of phosphorus and nitrogen.

Chemin also detected a slew of compounds, like authigenic magnetite, that only form in environments that have neutral pH and low salinity, that is: environments that are friendly to life as we know it here on Earth. All of this reinforces previous findings from the Rocknest sample, so it now seems Gale Crater was a big lake with water so nice you could drink it.

On top of that vacation resort image it seems the lake had been there for a really long time, which is a good attribute if you're trying to like, live and evolve in it.

Mission specialists used Chemin to measure the levels of various isotopes in the Rocknest sample to determine the amount of weathering that it had undergone. They estimated that it formed about 4.1 million years ago. All the results were the same for the John Klein and Cumberland, suggesting that the whole area was covered with water at that time. And geologists studied photos of Yellowknife Bay and Sheepbed, and found a complex layering of features, like nodules and ridges, suggesting that Gale Crater had a long, complex affair with water. So, they think that the lake lasted for tens of thousands, and possibly hundreds of thousands of years. So given all that time and a large lake rich in mineral energy, what kind of life could have materialized?

Chemolithoautotrophs are simple organisms that derive their energy from mineral compounds. Sounds a little bit weird, maybe, but on Earth these extremophiles can be found in lots of places. They tend to do especially well in unspeakably hot or dark places like caves and thermal vents where no other organisms dare to dwell.

So even though there is still no sign of life, past or present, on Mars, and I wanna be clear about that, the new results from Gale Crater add to evidence that Mars could once have boasted something like them. With these new results it seems like signs of past habitability are being found across bigger and bigger areas and longer stretches of time. Which means that with each new result we get closer to that last remaining step of actually finding signs of past life on Mars. I'm holding out hope. Curiosity, think you could do it?

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