A deep, dark secret may be lying in the heart of Pluto, literally. Scientists think that a vast ocean of liquid water underneath the heart-shaped feature on Pluto’s surface could possible harbor alien life, adding it to the very short list of cosmic bodies within our reach that might yield the discovery of extraterrestrial life, albeit in microbial form.

The findings, published last month in the journal Nature, is based on data from the NASA New Horizons spacecraft. The data suggests that chemicals in the water ocean keep it at a slushy consistency despite the fact that the temperatures are below freezing, and while that isn’t exactly the best condition for life to exist, life has shown that it can be found in some surprisingly harsh places here on Earth.

It could be one of the biggest discoveries of the NASA New Horizons spacecraft, which conducted a historic flyby of the dwarf planet back in July 2015, and has since headed out into the outer reaches of the solar system to explore some objects in the Kuiper Belt.

“In fact, New Horizons has detected ammonia as a compound on Pluto’s big moon, Charon, and on one of Pluto’s small moons. So it’s almost certainly inside Pluto,” William McKinnon, professor of earth and planetary sciences in Arts & Sciences at Washington University in St. Louis, said in a statement. “What I think is down there in the ocean is rather noxious, very cold, salty and very ammonia-rich — almost a syrup.

“It’s no place for germs, much less fish or squid, or any life as we know it,” he added. “But as with the methane seas on Titan — Saturn’s main moon — it raises the question of whether some truly novel life forms could exist in these exotic, cold liquids.”