On April 17, the Sun released a coronal mass ejection (CME), a gargantuan release of plasma coming from an active region of the solar surface. When these CMEs happened to be aimed at Earth, there’s always the risk that they will produce a geomagnetic storm affecting satellites and other electronics across the planet.
This time the “target” is not Earth but Mars. The wave of plasma was sent in its general direction and hit the Red Plant between April 21 and April 22. As far as CMEs go, this was actually quite a slow one moving between 700 and 800 kilometers per second (1.5 and 1.8 million miles an hour).
The CME was tracked by NASA’s STEREO-A and by SOHO, a collaborative mission between NASA and the European Space Agency. The space agency constantly tracks solar activity to better understand our star. It is also important to know if a CME is coming our way as it could put spacecraft and even astronauts in danger.

Mars has no astronauts (for now) but plenty of robotic explorers and orbiting satellites. And it hasn’t even got a magnetic field to shield them from it like Earth. Luckily, this CME was nothing to worry about and there was no precautions needed to be taken.
Mars has quite the week. A big CME and a little rotocraft from Earth took two flights from its surface in the last five days.