NASA identifies the cause of Mars' "water shortage"

After nearly a decade of orbiting Mars, NASA's MAVEN spacecraft has for the first time directly observed a process that scientists have long suspected was the main culprit in the Red Planet's loss of atmosphere.

The discovery could help answer the big question of how Mars transformed from a potentially habitable world with rivers and lakes into the icy, nearly airless desert it is today.

Although Mars is currently dry and cold, its surface bears undeniable evidence of a much wetter past.

Topographic features such as ancient river valleys, shallow lake beds, and minerals that form only in the presence of water suggest the existence of long-lasting lakes, perhaps even shallow seas, on the surface of Mars billions of years ago.

However, for liquid water to exist, Mars would need a much denser atmosphere to retain heat and maintain higher surface pressure.

Over the past decade, scientists have accumulated evidence that solar wind – a constant stream of ionized particles emitted from the Sun – and radiation have eroded much of Mars' atmosphere.

One of the most important mechanisms behind this erosion is a process called “sputtering,” in which high-energy particles from the solar wind collide with the planet’s upper atmosphere, imparting enough energy to neutral atoms to escape Mars’s gravity and fly into space.

“It’s like doing a ‘bomb’ dive into a swimming pool (holding your knees to get the most impact on the water surface),” said Shannon Curry, principal investigator of the MAVEN mission at the University of Colorado Boulder and lead author of the new study. “In this case, the ‘bomb’ is heavy ions from the Sun hitting the atmosphere very quickly and knocking out neutral atoms and molecules.”

Although sputtering has long been considered a key factor in Mars' climate change, this is the first time the process has been directly observed.

Using nine years of data collected by the MAVEN spacecraft, Curry and her colleagues captured the sputtering phenomenon that is occurring on Mars today.

These results establish the role of sputtering in the loss of Mars' atmosphere and in determining the history of water on Mars, according to Ms. Curry.

To fully determine whether sputtering is indeed the primary driver of Mars' long-term climate change, scientists will need to look back billions of years into the past using models, isotopic data, and ancient climate clues./.

(Vietnam+)

Source: https://www.vietnamplus.vn/nasa-xac-dinh-nguyen-nhan-sao-hoa-can-nuoc-post1042485.vnp