This image from NASA's Mars Reconnaissance Orbiter (MRO) shows the location with the most impressive known gully activity in Mars' northern hemisphere. / NASA

Scientists are re-thinking how to go about finding life on Mars, per a Scientific American dispatch from a recent conference of astrobiologists, geologists and others.

Key takeaways:

  • Maybe we don't have to find life in water. Here on Earth, there are organisms that can survive without water for years and come back to life when conditions are wetter.
  • We may have to drill into Mars to find evidence of past life. Yesterday, astrobiologists reported finding fossils of primitive microbes on Earth in what is today a hot, dry region of Australia that once had hot springs. Mars could have had the same environment in its past.
  • Microorganisms may have traveled between Mars and Earth on meteorites. Robert Hazen told me yesterday it is entirely plausible that life could have arrived here from Mars but, given the Sun's gravitational pull, it is unlikely it traveled the other direction.

Go deeper

Amy Harder, author of Generate
37 mins ago - Energy & Environment

Climate change goes mainstream in presidential debate

Photo illustration: Aïda Amer/Axios. Photo: Olivier Douliery-Pool/Getty

The most notable part of Thursday’s presidential debate on climate change was the fact it was included as a topic and assumed as a fact.

The big picture: This is the first time in U.S. presidential history that climate change was a featured issue at a debate. It signals how the problem has become part of the fabric of our society. More extreme weather, like the wildfires ravaging Colorado, is pushing the topic to the front-burner.

Finally, a real debate

Photo: Morry Gash/AP

A more disciplined President Trump held back from the rowdy interruptions at tonight's debate in Nashville, while making some assertions so outlandish that Joe Biden chuckled and even closed his eyes.

  • A Trump campaign adviser told Axios: "He finally listened." 

The result: A real debate.

Biden to Trump: "I have not taken a penny from any foreign source ever in my life"

Former VP Joe Biden pushed back Thursday against allegations from President Trump, saying he had never profited from foreign sources. "Nothing was unethical," Biden told debate moderator Kristen Welker about his son Hunter's work in Ukraine while he was vice president.

Why it matters: Earlier on Thursday, Hunter Biden's former business partner, Tony Bobulinski, released a statement saying Joe Biden's claims that he never discussed overseas business dealings with his son were "false."