Illustration of the Hubble Space Telescope (HST) observing a total lunar eclipse. In January 2019, astronomers used the total lunar eclipse to measure the amount of ozone in the Earth's atmosphere. They used the Moon as a mirror to reflect sunlight from Earth's atmosphere back into the HST. This allowed them to prepare for measuring the atmospheres of exoplanets and searching for signs of life. It was also the first time that a total lunar eclipse was observed by a space telescope.