(ORDO NEWS) — Taking advantage of the total lunar eclipse, astronomers using the Hubble Space Telescope discovered a sun-protective layer in the Earth’s atmosphere – ozone. The new method defines how astronomers and astrobiological researchers will seek evidence of life beyond Earth.
It is noteworthy that Hubble did not conduct direct observations of the Earth. Instead, astronomers used the moon as a mirror to reflect sunlight that passed through Earth’s atmosphere and then bounced back towards the space telescope. Using this method to observe eclipses reproduces the conditions under which future telescopes would measure the atmospheres of transiting exoplanets. These atmospheres may contain chemicals of interest to astrobiology and the study and search for life.
Despite the fact that numerous ground-based observations of this kind have already been carried out, this is the first time that a total lunar eclipse has been recorded in the ultraviolet wavelength range and using a space telescope. Hubble has found a strong spectral fingerprint of ozone that absorbs some of the sunlight. Ozone is essential to life because it protects the Earth’s atmosphere.
Photosynthesis on Earth, taking place for billions of years, is the reason for the high levels of oxygen on our planet and the presence of a thick ozone layer. This is one of the reasons why scientists believe that ozone or oxygen can be a sign of life on another planet, and they call them biosignatures.
Despite the fact that ozone in the Earth’s atmosphere was detected during previous ground-based observations during lunar eclipses, the Hubble study represents the strongest detection of a molecule to date.
Hubble recorded ozone absorbing some of the sun’s ultraviolet radiation that passed over the edge of the Earth’s atmosphere during a lunar eclipse that occurred from January 20 to 21, 2019. Several other ground-based telescopes also performed spectroscopic observations at other wavelengths during the eclipse, and were able to detect other components of the Earth’s atmosphere: oxygen and methane.
The atmospheres of some planets outside the solar system can be explored if an alien world crosses the obverse of its parent star – an event called a transit. During transit, starlight is filtered through the exoplanet’s atmosphere. (When viewed up close, the planet’s silhouette will appear as if there is a thin luminous “halo” around it caused by the illuminated atmosphere, just like the Earth when viewed from space).
However, detecting ozone in the sky of a rocky exoplanet does not guarantee the existence of life on the surface. According to scientists, other spectral signatures are needed in addition to ozone to infer the existence of life on the planet, and these signatures cannot necessarily be seen in ultraviolet light.
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