NASA discovers 'proton aurora' that sucks out water from the Martian surface

According to a new study that can help track water loss from Mars' atmosphere, a type of aurora has been identified as the most common form of the lights occurring on the red planet. Researchers say the proton aurora happens during the day and gives off ultraviolet light and can perhaps be the reason why the planet is dry. Auroras are commonly seen on Earth as colourful displays of light in the night sky near the polar regions like Norway and Antarctica. 

According to researchers from NASA's Goddard Space Flight Center (GSFC), the proton aurora is invisible to the human eye but detectable to the Imaging UltraViolet Spectrograph (IUVS) instrument on the MAVEN – Mars Atmosphere and Volatile Evolution –spacecraft. MAVEN's mission is to investigate how Mars lost much of its atmosphere and water, transforming its climate from one that might have supported life to one that is cold, dry, and inhospitable.

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Aurora possible through hydrogen

The proton aurora is generated indirectly by hydrogen derived from Martian water which is in the process of being lost to space. Hence scientists say this aurora could be used to help track ongoing Martian water loss. "In this new study using MAVEN/IUVS data from multiple Mars years, the team has found that periods of increased atmospheric escape correspond with increases in proton aurora occurrence and intensity," Andrea Hughes of Embry-Riddle Aeronautical University in the US said.

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Physics behind ultraviolet aurora

As per the study, the proton aurora is formed when sub-atomic particles, protons, from solar winds interact with the upper atmosphere on the dayside of Mars. Approaching Mars, the researchers explained that these protons transform into neutral atoms by stealing electrons from hydrogen atoms in a huge gas cloud surrounding the Red Planet. When the high-speed incoming atoms from the Sun hit the Martian atmosphere, some of their energy is emitted as ultraviolet light.

During southern summer on Mars, the red planet is near its closest distance to the Sun in its orbit and huge dust storms can occur. The summer warming and dust activity seem to cause proton auroras by forcing water vapour high in the atmosphere. These water molecules are broken by the solar extreme ultraviolet light into its two components – hydrogen and oxygen.

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The researchers explained that the light hydrogen is weakly bound by Mars' gravity and enhances the hydrogen gas cloud surrounding Mars, increasing the element's loss to space. "Also, the connection between MAVEN's observations of increased atmospheric escape and increases in proton aurora frequency and intensity means that proton aurora can actually be used as a proxy for what's happening in the hydrogen corona surrounding Mars. And therefore, a proxy for times of increased atmospheric escape and water loss," Hughes added.

The study by GSFC noted that as the hydrogen interactions with solar-wind protons become more common, the Martian aurora becomes more frequent and brighter. "Perhaps one day, when interplanetary travel becomes commonplace, travellers arriving at Mars during southern summer will have front-row seats to observe Martian proton aurora majestically dancing across the dayside of the planet. These travellers will witness firsthand the final stages of Mars losing the remainder of its water to space," Andrea Hughes said.

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(With PTI inputs)