The Solar Wind is Stripping Oxygen and Carbon Away From Venus

Artist's impression of the European Space Agency/JAXA BepiColombo mission in operation around Mercury. Credit: Astrium

The BepiColombo mission, a joint effort between JAXA and the ESA, was only the second (and most advanced) mission to visit Mercury, the least explored planet in the Solar System. With two probes and an advanced suite of scientific instruments, the mission addressed several unresolved questions about Mercury, including the origin of its magnetic field, the depressions with bright material around them (“hollows”), and water ice around its poles. As it turns out, BepiColombo revealed some interesting things about Venus during its brief flyby.

Specifically, the two probes studied a previously unexplored region of Venus’ magnetic environment when they made their second pass on August 10th, 2021. In a recent study, an international team of scientists analyzed the data and found traces of carbon and oxygen being stripped from the upper layers of Venus’ atmosphere and accelerated to speeds where they can escape the planet’s gravitational pull. This data could provide new clues about atmospheric loss and how interactions between solar wind and planetary atmospheres influence planetary evolution.

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The Solar Wind Whistles as it Passes Mercury

Image of chorus wave generation on Mercury. Credit: NASA/JHUAPL/Carnegie Institution of Washington

Mercury is the closest planet to our Sun, ranging from 46 million km (28.58 million mi) at perihelion to 69.82 million km (43.38 million mi) at aphelion. Because of its proximity, Mercury is strongly influenced by the steam of plasma constantly flowing from the Sun to the edge of the Solar System (aka. solar wind). Beginning with the Mariner 10 mission in 1974, robotic explorers have been sent to Mercury to measure how solar wind interacts with Mercury’s magnetic field to produce whistler-mode chorus waves – natural radio emissions that play a key role in electron acceleration in planetary magnetospheres.

In addition to being the cause of geomagnetic storms and auroras in planetary atmospheres, these waves also lead to electromagnetic vibrations at the same frequencies as sound, producing chirps and whistles. In a recent study, an international research team consulted data from the BepiColombo International Mercury Exploration Project, which gathered data on Mercury’s magnetosphere during its first and second flyby. Their results are the first direct probing of chorus waves in Mercury’s dawn sector, which showed evidence of possible background variations in magnetic field.

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