PASADENA, Calif. (NASA PR) — A new study shows how the chemicals in an exoplanet’s atmosphere can, in some cases, reveal whether or not the temperature on its surface is too hot for liquid water.

In our solar system, planets are either small and rocky (like Earth) or large and gaseous (like Neptune). But around other stars, astronomers have found planets that fall in between – worlds slightly larger than Earth but smaller than Neptune. These planets may have rocky surfaces or liquid-water oceans, but most are likely to be topped with atmospheres that are many times thicker than Earth’s and opaque.

The new science results indicate that a large quantity of the Red Planet’s water is trapped in its crust rather than having escaped into space.

PASADENA, Calif. (NASA PR) — Billions of years ago, according to geological evidence, abundant water flowed across Mars and collected into pools, lakes, and deep oceans. New NASA-funded research shows a substantial quantity of its water – between 30 and 99% – is trapped within minerals in the planet’s crust, challenging the current theory that due to the Red Planet’s low gravity, its water escaped into space.

Early Mars was thought to have enough water to have covered the whole planet in an ocean roughly 100 to 1,500 meters (330 to 4,920 feet) deep – a volume roughly equivalent to half of Earth’s Atlantic Ocean. While some of this water undeniably disappeared from Mars via atmospheric escape, the new findings, published in the latest issue of Science, conclude it does not account for most of its water loss.