NASA's MAVEN Reveals Most of Mars' Atmosphere Was Lost to Space

https://www.nasa.gov/news/releases/latest/index.html

Solar wind and radiation are responsible for stripping the Martian atmosphere, transforming Mars from a planet that could have supported life billions of years ago into a frigid desert world, according to new results from NASA’s MAVEN spacecraft.
Source: Solar System News
NASA’s MAVEN Reveals Most of Mars’ Atmosphere Was Lost to Space
Solar System News