Earth seen from orbit at night. Photo: NASA

The Hubble Space Telescope observed Earth as future tools could one day see a distant, alien planet.

Why it matters: These kinds of analogous experiments using Earth in place of an exoplanet (a world orbiting another star) give scientists a chance to see what a habitable planet may look like through telescopes if one is eventually found.

What they did: Researchers used the Hubble Space Telescope to observe the Earth during a total lunar eclipse, allowing the storied telescope to detect ozone, a gas thought to be key to the evolution of life, in our planet's atmosphere.

  • The scientists behind the observations — detailed in a study due to be published in the Astronomical Journal — used the Hubble to look at light that had been filtered through Earth's atmosphere reflected from the Moon.
  • That allowed the researchers to parse out the makeup of our planet's atmosphere in much the same way as future missions could when observing a planet passing across the face of its star.
  • "We want to make sure we know what the Earth, the only habitable and inhabited planet we know of, looks like using the same methods astronomers use for exoplanets," Allison Youngblood, one of the authors of the new study, told me via email.

What's next: Scientists don't yet have the tools in orbit to confirm the discovery of a habitable planet orbiting a distant star, but future missions could one day confirm another Earth-like planet out there in the galaxy.

Go deeper

Miriam Kramer, author of Space
Sep 15, 2020 - Science

A return to Venus

Illustration: Annelise Capossela/Axios

The discovery of possible sign of life on Venus is buoying a push by many in the planetary science community to get NASA and other space agencies to send missions to Venus that could sniff out if there really is life there.

Why it matters: NASA hasn't sent a dedicated spacecraft to study Venus from close range in about 30 years, with much of the hunt for life in the solar system focusing instead on Mars.

How "naked ballots" could upend mail-in voting in Pennsylvania

Trump signs in Olyphant, Penn. Photo: Eric Baradat/AFP via Getty Images

Pennsylvania's Supreme Court ordered state officials last week to throw out mail-in ballots submitted without a required inner "secrecy" envelope in November's election, the Philadelphia Inquirer reports.

The state of play: The decision went under the radar alongside the simultaneous decision to extend the time that mail-in ballots could be counted, but Philadelphia's top elections official warned state legislators this week that throwing out so-called "naked ballots" could bring "electoral chaos" to the state and cause "tens of thousands of votes" to be thrown out — potentially tipping the presidential election.

Commission releases topics for first presidential debate

Moderator Chris Wallace. Photo: Drew Angerer/Getty Images

Fox News anchor Chris Wallace has selected what topics he'll cover while moderating the first presidential debate between President Trump and former Vice President Joe Biden next week.

What to watch: Topics for the Sept. 29 debate will include Trump and Biden's records, the Supreme Court, COVID-19, economic policy, racism and the integrity of the election, the Commission for Presidential Debates announced on Tuesday. Each topic will receive 15 minutes of conversation and will be presented in no particular order.

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