Despite mysterious lights and formations on Ceres and an ice-covered sea on Europa, Mars continues to be our best bet for finding evidence of current or past alien life beyond Earth. That possibility just got a little brighter on Monday, when researchers from the University of Glasgow announced that they found small amounts of so-called “fire opal” buried within Nakhla meteorite, which fell to Earth from Mars in 1911.

Sadly, the presence of opal doesn’t isn’t a sign that ancient Martians were mining their planet for precious gemstones. What it does mean, however, was that water was definitely present in some quantities at one time. Fire opal, in particular, requires the presence of water to form, and is often formed near thermal springs, which are often teeming with life here on Earth.

“Firstly, it definitively confirms findings from NASA’s imaging and exploration of the Martian surface which appeared to show deposits of opal. This is the first time that a piece of Mars here on Earth has been shown to contain opal,” said Professor Martin Lee, of the University’s School of Geographical and Earth Sciences

“Secondly, we know that on Earth opals like these are often formed in and around hot springs. Microbial life thrives in these conditions, and opal can trap and preserve these microbes for millions of years. If Martian microbes existed, it’s possible they too may be preserved in opal deposits on the surface of Mars.”

The same team already learned in 2013 that water had once dissolved the surface of Mars, when they found traces of secondary minerals created when water interacted with the minerals olivine and augite, contained within the same Nakhla meteorite.

The total piece of the meteorite they worked with this time is small, just 1.7 grams. The fire opal discovery required the use of a powerful scanning electron microscope.