When Size Matters
The scientific community agrees that Mars had flowing water at some point in its history and recently scientists determined what exactly caused the water to vanish: the planet’s small size, NPR reported.
Mars is about half the size of the Earth and has slightly more than one-tenth of the mass.
In their study, the research team suggested that the red planet’s low mass and gravity made it easier for volatile elements and compounds to escape from the surface into space.
They studied 20 Martian meteorites dating back 200 million years to four billion years. They focused on the ratio of two potassium isotopes – potassium-39 and potassium-41 – found in the space rocks.
Their findings showed that Mars’ lower gravity caused the lighter potassium-39 to return to space unlike the heavier potassium-41. Water would have also behaved the same way, which means it disappeared during the planet’s formation.
The team also analyzed potassium isotopes from the moon and an asteroid – both of which are smaller and drier than the Earth and Mars. They again found a direct correlation between mass and the volatiles – or lack thereof – in the samples.
“Mars’ fate was decided from the beginning,” co-author Kun Wang said in a statement.
Other researchers, meanwhile, said the study could help astronomers fine-tune their search for other habitable exoplanets.
“This does probably indicate a lower limit on size for a planet to be truly habitable,” Bruce Macintosh, who was not involved in the study, told NPR.
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