Astronomers use Hubble to detect ozone on Earth

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Using the Hubble Space Telescope, scientists have shown that it will be possible to detect ozone in the atmospheres of exoplanets, using larger telescopes while observing transits of those exoplanets across the face of their star.

What the scientists did was aim Hubble at the Moon during a lunar eclipse. Moreover, they timed the observations so that the sunlight hitting the Moon and reflecting back to Earth (and Hubble) had also traveled through the Earth’s atmosphere on its way to the Moon.

They then looked at the spectrum of that light, and were able to glean from it the spectral signal of ozone in the Earth’s atmosphere. When giant ground-based telescopes under construction now come on line in the coming decades they will have the ability to do this with transiting exoplanets.

The measurements detected the strong spectral fingerprint of ozone, a key prerequisite for the presence – and possible evolution – of life as we know it in an exo-Earth. Although some ozone signatures had been detected in previous ground-based observations during lunar eclipses, Hubble’s study represents the strongest detection of the molecule to date because it can look at the ultraviolet light, which is absorbed by our atmosphere and does not reach the ground. On Earth, photosynthesis over billions of years is responsible for our planet’s high oxygen levels and thick ozone layer. Only 600 million years ago Earth’s atmosphere had built up enough ozone to shield life from the Sun’s lethal ultraviolet radiation. That made it safe for the first land-based life to migrate out of our oceans.

“Finding ozone in the spectrum of an exo-Earth would be significant because it is a photochemical byproduct of molecular oxygen, which is a byproduct of life,” explained Allison Youngblood of the Laboratory for Atmospheric and Space Physics in Colorado, USA, lead researcher of Hubble’s observations.

Ozone does not guarantee the presence of life on an exoplanet, but combined with other detections, such as oxygen and methane, would raise the odds significantly.


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  • LocalFluff

    I didn’t think that the Hubble was allowed to turn even to 90 degrees from Earth. Because the bright light reflected would destroy its instruments. That’s what restricts Hubble in LEO: never point at Earth, never point at the Moon, never point at the Sun. And all with 90 degrees safety margin, so that no blending light can possibly reflect into the tube of the glass.

    That’s an advantage of an L2 orbit, that the Earth is but a tiny orb and Luna insignificant.

  • Brad

    That’s very exciting. A large UV space telescope should be an easier project than JWST, shouldn’t it?

    JWST was constrained by the 5.4 meter diameter payload shroud of Ariane V, and the extreme measures needed to cool the JWST for IR sensing.

    How large a mirror would be needed for the job? The New Glenn with its 7 meter payload shroud could fit a 6.5 meter sized mirror such as the JWST without any complicated folding mechanism.

  • LocalFluff

    @Brad One could line up multiple mirrors each with the fairing diameter, throughout the fairing length. When in space, rotate them and with interferometry in effect have a mirror with the resolution (but not the sensitivity) of a mirror with the length of the mirror line as its diameter.

    Interferometry in visual light is only used at a couple of ground based telescopes such as Keck, and still requires heavy equipment. When interferometry becomes space borne, some discoveries will be made for sure. It could of course be used on detached mirrors, it’s a matter of precision optics to make it work at greater distances. Radio interferometry has already been applied, so perhaps soon one can go to the microwaves, then infrared. As clever ways are found to line up the tiny phases of those photons.

  • LocalFluff

    LISA will in the mid 2030s measure gravity waves. Three satellites will measure the distances to each other with laser. If the phases of the lasers change, that means that spacetime between them has been curved. If such super precision measurements are possible in the 2030s, for sure simple visual och UV interferometry will be a walk in the park in comparison!

    We will have Solar system wide telescopes, resolution wise, with individual mirrors distributed in different orbits. We could by radio tell the Vogons that they have parked their car improperly (c’est genant de garre ici). Earth will be known as the evil big sister of the galaxy. Just put the leftists on the microphone and they will piss everyone off.

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