Mars’ Atmosphere Swells Nearly 4 Times Its Usual Size Without Solar Wind

Mars's atmosphere is as thick, if not wider, than Earth's. However, researchers noticed that it noticeably swelled after a constant solar wind.

Mars' Atmosphere Swell

Every second, the solar wind's swift stream of charged particles regularly blasted from the sun and permeated the solar system, even reaching beyond Pluto, pushing away about 0.25 lbs (0.11 kg) of Mars' atmosphere.

But some of that wind disappeared in December for two days. The abrupt and dramatic disappearance caused the atmosphere on Mars' side facing the sun to expand from 497 miles (800 km) to over 1,864 miles (3,000 km), about four times its normal size.

Mars Atmosphere and Volatile Evolution (MAVEN) is a NASA orbiter monitoring Mars's atmosphere and its reaction to changes in the sun's activity since 2014. It captured the unusual occurrence.

Other features of the Martian system revealed by MAVEN's data included the ionosphere expanding similarly to the bow shock, the teardrop-shaped magnetosphere, and the bow shock.

"We're really off the charts here," Jasper Halekas, a professor of physics and astronomy at the University of Iowa and a member of the MAVEN team, said at the AGU conference being held this week in California and online on Monday. "This is something we haven't seen at Mars before with MAVEN."

Halekas and his colleagues investigated how major solar events influence the planet's atmosphere using MAVEN's data on the unexpected dynamics on Mars. This knowledge is crucial to comprehending the planet's evolution. The scientists revealed the results on Monday. They also have ramifications for our knowledge of Earth-like planets outside our solar system and their interactions with their host stars.

The unusual event, which was the first in almost ten years of MAVEN's operation, happened when a solar wind's swifter portion passed its slower counterpart and sucked up its material, leaving a sparse area in its wake.

On Dec. 25, 2022, the depleted storm landed on Mars, providing scientists with an exciting up-close view of the planet's atmosphere expanding as if it were orbiting a less "windy" star.

"This was a Christmas present for us," said Halekas, leading a new study reporting this event. "Nature set up this perfect science experiment."

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How Does Solar Wind Affect Earth's Atmosphere?

The solar wind is an unceasing flow of protons and electrons from the corona - the sun's outermost atmosphere. As per the National Oceanic and Administration Space Weather Prediction Center (SWPC), these charged particles travel up to 500 miles per second (800 km/s) in a plasma state as they swiftly traverse the solar system.

A flurry of charged particles is sent into the magnetosphere and down the lines of Earth's magnetic field, towards the poles, by the solar wind as it arrives on Earth. Above the polar regions, these particles' interaction with Earth's atmosphere can result in brilliant aurora displays.

The Earth's magnetic field creates a magnetic "bubble" known as the magnetosphere above the uppermost layer of the atmosphere, often referred to as the ionosphere layer. The magnetosphere is a key element in human protection. It deflects and shields high-energy, damaging cosmic ray radiation constantly emitted during star explosions and traverses the universe. Another component that interacts with the magnetosphere is the solar wind, a stream of magnetic gas originating from the Sun.