The lunar eclipse earlier in January 2019 allowed astronomers using the NASA/ESA Hubble Space Telescope to detect ozone in the Earth’s atmosphere. 

It was the first time a total lunar eclipse was captured from a space telescope and the first time such an eclipse had been studied in ultraviolet wavelengths.

Hubble did not look at the Earth directly. Astronomers used the Moon as a mirror that reflects the sunlight that has been filtered through Earth’s atmosphere.

Using a space telescope for eclipse observations is cleaner than ground-based studies because the data is not contaminated by looking through the Earth’s atmosphere.

The method used by the astronomers helps in their quest in observing Earth-like planets around other stars in the search for life. 

Allison Youngblood of the Laboratory for Atmospheric and Space Physics in Colorado, USA, lead researcher of Hubble’s observations, said:

“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.”

Hubble recorded ozone’s ultraviolet spectral signature imprinted on sunlight that filtered through Earth’s atmosphere during a lunar eclipse that occurred on 20-21 January, 2019. Several other telescopes also made spectroscopic observations at other wavelengths during the eclipse, searching for more of Earth’s life-nurturing ingredients, such as oxygen, methane, water, and carbon monoxide.

 Antonio Garcia Munoz of the Technische Universität Berlin in Germany, said:

“This investigation clearly highlights the benefits of the ultraviolet spectroscopy in the characterization of exoplanets. It also demonstrates the importance of testing innovative ideas and methodologies with the only habitable planet that we know of to date!”

Hubble was launched way back in 1990 and it was never envisioned then that it would be used in this way showing how innovative these astronomers are today.

Allison Youngblood continued:

“”You would need other spectral signatures in addition to ozone to conclude that there was life on the planet, and these signatures cannot be seen in ultraviolet light.”

The upcoming NASA/ESA/CSA James Webb Space Telescope, an infrared observatory scheduled to launch in 2021, will be able to penetrate deep into a planet’s atmosphere to detect methane and oxygen.

This study was published in The Astronomical Journal