Mars as seen by the Curiosity rover. Photo: NASA/JPL-Caltech/MSSS

After decades of sending missions to Mars, NASA is now zeroing in on regions of the red planet that they think have the best chance of determining whether the world has hosted — or hosts — life.

The big picture: Scientists are now able to point to parts of Mars that were once likely wet and warm, with geological signatures similar to the rivers, deltas and lakes on Earth — upping the odds that those parts of Mars could have once been friendly to life.

"Habitable and inhabited are two very different questions. You can build a house and you can furnish it nicely and put food in the fridge, but that doesn't mean someone lives there."
— NASA's Melissa Trainer to Axios

Driving the news: A new study finds NASA's Mars 2020 rover will land in an area that could be the perfect place to hunt for the fossilized evidence of past life.

  • The landing site — known as the Jezero Crater — once was home to a long-lived lake and river delta billions of years ago.
  • The rim of the crater could be rich with carbonates, which can help preserve signs of ancient life in fossilized form.
  • The Mars 2020 rover is expected to investigate the possible rock deposits and explore the delta that once fed the lake in the crater.

Meanwhile: Last week, NASA announced that Curiosity — which found Mars was habitable for microbial life in the past — detected a small amount of oxygen on Mars, but no one is quite sure where it's coming from.

  • The discovery adds to the mystery around the rover's possible detection of methane also reported earlier this year.

Yes, but: It's possible methane and oxygen could have been created through natural geological processes that have nothing to do with life.

  • Finding the origins of these molecules is exceedingly difficult, scientists say, without other pieces of evidence that point to living things on Mars.
  • Parsing out whether a methane molecule came from a living thing or geology could involve digging into its isotopic composition, but even then, it's not a sure-fire way to confirm the origins of the detection, scientists say.
  • The 2020 rover is planning to cache rock samples for eventual return to Earth on a future mission in order to confirm any possible discovery that points to life.
"There's always this uncertainty when we look at Mars."
— NASA scientist Lindsay Hays to Axios

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Updated 2 hours ago - Politics & Policy

Coronavirus dashboard

Illustration: Aïda Amer/Axios

  1. Politics: Chris Christie: Wear a mask "or you may regret it — as I did" — Senate Democrats block vote on McConnell's targeted relief bill.
  2. Business: New state unemployment filings fall.
  3. Economy: Why the stimulus delay isn't a crisis (yet).
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Early voting eclipses 2016 total with 12 days until election

People stand in line to vote early in Fairfax, Virginia in September. Photo: Tasos Katopodis/Getty Images

Americans have cast more than 47.1 million ballots in the 2020 presidential election, surpassing the total early-vote count for 2016 with 12 days left until Election Day, according to a Washington Post analysis of voting data.

Why it matters: The election is already underway, as many states have expanded early and mail-in voting options because of the coronavirus pandemic.

What to expect from the final debate of the 2020 election

Trump and Biden at the first debate. Morry Gash-Pool/Getty Image

Watch for President Trump to address Joe Biden as “the big guy” or “the chairman” at tonight's debate as a way of dramatizing the Hunter Biden emails. Hunter's former business partner Tony Bobulinski is expected to be a Trump debate guest.

The big picture: Trump's advisers universally view the first debate as a catastrophe — evidenced by a sharp plunge in Trump’s public and (more convincingly for them) private polling immediately following the debate.