This finding offers new insights into the possibility of water-rich planets throughout our galaxy.

GJ 9827d, a planet no bigger than twice the diameter of Earth, has caught the attention of astronomers due to the potential for a water-rich atmosphere. While exciting, the scorching conditions on the planet, with temperatures reaching 800 degrees Fahrenheit, make it an inhospitable, steamy world akin to Venus.

The significance lies in the fact that this marks the first time that astronomers have directly detected a water-rich atmosphere on a planet through atmospheric measurements. The team involved in the research, including scientists from the Trottier Institute for Research on Exoplanets at Université de Montréal and the Max Planck Institute for Astronomy in Heidelberg, Germany, considers this a crucial step in determining the prevalence and diversity of atmospheres on rocky planets.

According to Björn Benneke, a team member from the Trottier Institute for Research on Exoplanets, this discovery allows them to demonstrate the existence of water-rich atmospheres on planets around other stars, which is of great interest in the search for alien life.

Laura Kreidberg, a co-principal investigator from the Max Planck Institute for Astronomy, adds that the detection of water on a planet as small as GJ 9827d is a landmark achievement. It brings us closer to characterizing truly Earth-like worlds outside our solar system.

However, it is too early to determine whether the water vapor detected is part of a hydrogen-rich atmosphere or if the entire atmosphere consists mostly of water. The team is still investigating whether GJ 9827d is a mini-Neptune with a hydrogen-rich atmosphere or a warmer version of Jupiter's moon Europa, with a substantial amount of water beneath its rocky crust.

The Hubble Space Telescope's observing program, led by principal investigator Ian Crossfield from Kansas University, was designed specifically to identify water vapor in the planet's atmosphere. Pierre-Alexis Roy, the lead author of the science paper from the Trottier Institute for Research on Exoplanets, clarifies that either result would be significant, indicating the potential for water-rich atmospheres on small planets.

The team conducted observations over a three-year period, observing 11 transits where GJ 9827d crossed in front of its host star. During these transits, the planet's atmosphere filtered starlight and revealed the spectral fingerprints of water molecules. This allowed Hubble to investigate water vapor above potential clouds on the planet.

Thomas Greene, an astrophysicist from NASA's Ames Research Center, shares that observing water vapor is a gateway to discovering other elements and provides opportunities for future study. He highlights the upcoming James Webb Space Telescope, which will be able to conduct additional infrared observations and detect carbon-bearing molecules such as carbon monoxide, carbon dioxide, and methane. This will further enhance our understanding of not only GJ 9827d but also other similar planets.

GJ 9827d was first discovered by NASA's Kepler Space Telescope in 2017. It orbits a red dwarf star in the constellation Pisces, located 97 light-years away from Earth.

This groundbreaking finding by the Hubble Space Telescope, a collaborative project between NASA and ESA, opens up new avenues for understanding the existence and characteristics of water-rich planets in our galaxy. With further exploration, scientists hope to uncover more about these intriguing worlds and expand our understanding of the potential for life beyond Earth.