The European Space Agency (ESA) announced that Hubble has observed a total lunar eclipse, becoming the first space telescope to focus on the event. It was also the first time an eclipse was studied in ultraviolet wavelengths, per a study to be published in The Astronomical Journal.
The telescope was trained on the eclipse with a method that NASA and the ESA hope will serve “as a proxy for how they will observe Earth-like planets around other stars in the search for life.” During a total lunar eclipse, the alignment of the three bodies involved is similar to what happens when an exoplanet transits across its local star. So, for this study of Earth, Hubble only looked at the moon during an eclipse, observing the sunlight that has been filtered through Earth’s atmosphere to search for ozone.
However, there are significant challenges to training the telescope on our moon. “The moon is so close to Earth that Hubble had to try and keep a steady eye on one select region, to precisely track the moon’s motion relative to the space observatory,” the announcement said. “It is for these reasons that Hubble is very rarely pointed at the moon.”
The data detected “the strong spectral fingerprint of ozone” when using the moon as a mirror for Earth’s atmosphere. That’s important because it’s a key sign of the possibility of the development or presence of life. “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,” said Allison Youngblood, lead researcher of Hubble’s observations at the Laboratory for Atmospheric and Space Physics in Colorado.
It’s a great step, but it’s not sufficient to determine whether life exists on an exoplanet. The soon-to-launch James Webb Space Telescope (JWST) will be able to continue this research in new and exciting ways. “We expect JWST to push the technique of transmission spectroscopy to unprecedented limits,” said Antonio Garcia Munoz of the Technische Universität Berlin. “In particular, it will have the capacity to detect methane and oxygen in the atmosphere of planets orbiting nearby, small-sized stars. This will open the field of atmospheric characterization to increasingly smaller exoplanets.”
Between the launch of many Mars rovers in July, including NASA’s Perseverance, and studies like this, plenty of agencies are deep into the search of life beyond the barrier of Earth’s atmosphere.