Is THIS why Mars no longer has any liquid water on its surface? Scientists claim the Red Planet is too SMALL to retain moisture – casting doubt on its habitability

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  • Scientists study potassium levels on meteorites from Mars
  • They arrived millions of years ago and provide a detailed picture of the Red Planet
  • This allowed them to predict the levels of other volatile chemicals such as water.
  • They found that Mars, unlike Earth, lost most of its volatiles during the early days of its evolution.
  • However, it did not lose asteroids or even smaller bodies such as the Moon.
  • This suggests that size is an important factor in the planets’ chances of holding water.

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Mars once used to have liquid water, but it is now an arid desert landscape – and that may be because it is too small to retain moisture, according to planetary scientists.

About half the size of Earth, Mars is the second smallest planet in the Solar System, sitting at the very outer edge of the habitable zone where liquid water can ‘flow’.


There is ‘anecdotal evidence’ that liquid water was once flowing in the Red Planet, including at Jezero Crater, where the NASA Persistence rover is currently searching for ancient signs of life, but this study shows that it did not last long.

Senior author Dr. Kun Wang from Washington University in St. Louis and his colleagues studied the chemical makeup of Martian meteorites that have fallen to Earth.

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These rocks, millions to billions of years old, showed that the composition of Mars did not contain the chemicals necessary to hold water for long periods of time.

Mars once used to have liquid water, but it is now an arid desert landscape and this may be because it is too small to retain moisture, according to planetary scientists.

Mars: The Basics

Mars is the fourth planet from the Sun, with a ‘near-dead’ dusty, cold, desert world with a very thin atmosphere.

Mars is also a dynamic planet with weather, polar ice caps, canyons, extinct volcanoes and evidence that it was even more active in the past.

It is one of the most explored planets in the Solar System and the only planet humans have sent a rover to explore.

A day on Mars takes a little over 24 hours and a year is 687 Earth days.

Facts & Figures

orbital time: 687 days

surface area: 144.8 million km²

distance from the sun: 227.9 million km

gravity: 3.721 m/s

RADIUS: 3,389.5 km

moon: Phobos, Deimoso


Mars lost most of its volatile elements, according to Dr. Wang, who said these elements resulted in liquid water and other factors necessary for life.

Unlike Earth, which held onto its volatile elements, ‘Mars’ fate was decided from the beginning,’ Dr Wang explained.

It may be smaller in size, he said, with smaller planets less capable of holding these volatile elements and the resulting water.

“The size requirements of rock planets are likely to retain enough water to enable habitability and plate tectonics – with a mass greater than Mars,” Dr Wang said.

Water is an essential component of life ‘as we know it’ and there is ample evidence of water on Mars in its early history.

Previous studies have suggested that small worlds may contain more water in one large ocean than the entire Atlantic Ocean on Earth.

But there is no liquid water on the surface of Mars today.

Remote sensing studies and analysis of Martian meteorites from the 1980s suggest that Mars was once richer in water than Earth.

NASA’s Viking Orbiter spacecraft — and, more recently, Curiosity and Perseverance hovering over the ground — returned dramatic images of the Martian landscape marked by river valleys and flood channels.

Despite this evidence, no liquid water remains on the surface of the Red Planet.

Previous explanations for this lack of water have included a weakening of the magnetic field resulting in the loss of its atmosphere, allowing water to evaporate into space.

This new study, the discovery of trace chemicals such as potassium in Martian meteorites, suggests a more fundamental problem facing the Red Planet – size.

For the new study, Wang and his colleagues used stable isotopes of the element potassium (K) to estimate the presence, distribution and abundance of volatile elements on various planetary bodies.

Potassium is a moderately unstable element, but scientists decided to use it as a kind of tracer for more volatile elements and compounds, such as water.

While there has been evidence of surface water in the early years of Mars' history, today it is a desert-like landscape with no liquid water on its surface.

While there has been evidence of surface water in the early years of Mars’ history, today it is a desert-like landscape with no liquid water on its surface.

Mars rock samples suggest a once habitable environment

NASA said the first rocks collected by the Persistence rover show that Jezero Crater was once ‘a potentially habitable continuous environment’.

The news follows the rover’s successful mission earlier this week to collect two rock samples, named ‘Montdenier’ and ‘Montagnac’.

The lead samples appear to have a basaltic structure, which scientists say may have been formed from ancient lava flows and provide a timeline of the ancient lake – the time since it disappeared.

NASA already knows that the crater was once filled with water, but how long remains a mystery.

The changes scientists have observed in the rock suggest that groundwater was present for a long time.

The Ground team determined that there are salts within the rock samples that may have formed when groundwater flowed through and replaced the original minerals in the rock.

Or more likely when the liquid water evaporates, leaving the salts.

Samples will be returned to Earth for more detailed analysis in advanced laboratories over the next decade.


This is a new technique that uses potassium-to-thorium ratios gathered by remote sensing and chemical analysis to predict how volatiles once were on Mars.

In previous research, members of the research group used the potassium tracer method to study the formation of the Moon.

Wang and his team measured the potassium isotope compositions of 20 previously confirmed Martian meteorites, which represent most of the planet’s rock material.

Using this approach,…


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