Mars Had Liquid Water On Its Surface. Here are the reasons scientists believe it vanished
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All evidence supports the idea that Mars once had water. However, numerous flybys and orbiters as well as rovers have shown that any liquid water once found on Mars' surface is long gone.
Washington University in St. Louis may have discovered the reason. Mars is half the size of Earth and less than one-tenth as large as our watery world.
The Mars Ocean Hypothesis is one idea that suggests Mars had a lot of liquid water. Kun Wang, the co-author of the new study, says that his team's findings, published in the Proceedings of the National Academy of Sciences this week, cast cold water on that idea.
Wang, an assistant professor in Earth and Planetary Sciences, stated that Mars' fate was determined from the beginning. "There is likely to be a threshold on how large rocky planets must be to maintain enough water for habitability and plate-tectonics."
Because Mars' lower gravity and mass makes it easier to allow volatile elements and compounds, such as water, to escape its surface and into space.
Zhen Tian, a graduate student at Wang's laboratory, led the research team. They examined 20 Martian meteorites, which range in age from approximately 200 million years to 4 billion years. This was during a time when formation of the solar system was chaotic.
Researchers analysed potassium, a volatile element, to understand how water might have behaved on Mars' surface.
Wang spoke to NPR and said that the team measured the ratios of the two isotopes potassium potassium-39 (and potassium-41) in the meteorites. The potassium-39 is less likely to be lost to space in lower gravity environments like Mars. This is why it leaves behind the potassium-41, a heavier isotope. Water behaves the same way. This indicates that the majority of it was lost to space when Mars formed.
Wang and his colleagues noticed this in older meteorites. This suggests that Martian water was concerned from the beginning.
To study potassium isotopes, the team also examined samples from the moon, and an asteroid. Both were smaller and drier than Earth and Mars. The team found a direct correlation in the mass of the samples and the presence or absence of volatiles.
Wang states that the liquid water that was left on the Martian surface created the canyons, riverbeds, and other formations we see today. He notes that this water would have also disappeared if it hadn't been trapped as ice at Martian poles, as the planet's climate became colder.
These findings could be used to refine the search for habitable extraplanets
This research also has implications beyond our solar system. Scientists are searching for planets orbiting other stars in search of the holy grail: those that can support life without being too hot or too cold.
Even though a planet orbits its star in what is known as the Goldilocks Zone at the right distance to allow liquid water to flow, it may still be too small to hold onto the water.
Bruce Macintosh (deputy director, Stanford University's Kavli Institute for Particle Physics and Cosmology), said that this lower limit is likely to indicate that a planet can be considered habitable. Understanding that the lower limit is important, there are evidence lines that suggest that small planets are more frequent than large ones. If these small planets are dry, there may be fewer potential habitable worlds than we thought.
However, he says that "only the most optimistic exoplanetastronomers" would list a Mars-sized exoplanet for habitability.
