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Later decades of piece of work, NASA believes information technology has solved one of the most fundamental questions of how Mars became the dusty, arid planet that it is today. Over the past 15 years, rovers similar Spirit, Opportunity, and Curiosity have uncovered compelling evidence that Mars was in one case covered by a liquid ocean. This, in turn, implies that the planet was much warmer, maybe with an oxygen-rich atmosphere.

The trouble is, today's Mars bears piddling resemblance to the primordial planet it must have been. Mars' atmosphere is a fraction the density of Earth's — air pressure at the summit of Mount Everest (the highest point on World) is 4.89 PSI, while the air pressure at the bottom of Mars' Hellas Planitia (a 23,465-foot deep crater) is just 0.168 PSI. In other words, the air pressure at the highest point on our planet is 29x college than the air force per unit area at the lowest point on Mars.

At that place have been three principal hypotheses for how Mars might have lost its atmosphere: It'due south possible that Mars' atmosphere was eroded by solar air current, that much of the atmosphere was torn away by a cataclysmic touch, or that the low gravity of the planet allowed atmosphere to accident off and dissipate over time. These conditions are non mutually sectional, and it's possible that all three of them played a part, but NASA believes it has constitute sufficient prove to assign a primary cause. The culprit? Solar wind — specially the types of energetic blasts emitted by the sun during periods of unrest.

Blowing in the wind

In 2022, NASA'south Maven (Mars Atmosphere and Volatile Evolution Mission) arrived at Mars and began taking samples of the Red Planet's atmosphere. The probe found that Mars continues to lose significant amounts of its atmosphere fifty-fifty today, roughly one-quarter pound per 2d. The solar air current is comprised of highly charged particles moving at a million miles an hour or more. When those particles strike the Martian atmosphere, they create an electric field, supercharging ions in the Martian atmosphere and sending them rocketing into space.

This same process occurs on Earth as well (and we've written nigh the devastating bear on a massive solar storm could have on our planet's infrastructure), but ordinary solar activity doesn't crusade modern life much trouble. That'due south thank you to the magnetic field that sheaths our planet. Mars, in contrast, has merely the remnants of a magnetic field, as shown in the prototype below:

EarthvsMars

The blue and red areas are the spots on Mars still shielded by a fractional magnetic field.

Maven observed that periods of increased solar activity and solar storms sharply increased the rate at which Mars lost atmosphere. The video beneath shows how Mars loses temper — 25% is lost from a polar plume, while 75% of the loss occurs at the long tail.

The sun has been a main sequence star for billions of years, but we know that it can undergo periods of greater and bottom activity. A Carrington-level outcome that struck Mars instead of Earth could accept done colossal damage. Given that such events occur oft on stellar fourth dimension scales (a Carrington-level event hits Earth roughly every 500 years), Mars' atmosphere wasn't just diluted — information technology was violently wrenched away.

These findings could sharpen our ain search for planets likely to harbor life. Potent, planet-broad magnetic fields appear nearly essential for protecting the environment required to sustain life. The remains of Mars' magnetic field were nowhere near strong plenty to shield the planet, and without that protection, planets may not be able to hold on to the temper required to maintain temperatures above freezing. It could also have implications for whatever programme to terraform the planet — without a magnetic field in place, it could prove difficult to generate a sustainable atmosphere. Given that whatever long-term terraforming projection of this nature would take millennia, nonetheless, scientists should have plenty of fourth dimension to consider the trouble.