A SUNSPOT SO BIG YOU CAN SEE IT FROM MARS: A huge sunspot (AR3363)  just emerged over the sun’s southeastern limb. Mars rover Perseverance saw it before we did. On July 2nd, the rover’s mast-mounted stereo camera (MASTCAM-Z) tilted up to the sky above Jezaro crater and photographed a deep-black dot on the solar disk:

Zoran Knez of Croatia assembled this montage using publically available NASA images

Perseverance does this all the time. Using a solar filter, the rover looks at the sun almost every day to check its brightness. When the sun dims, researchers know a dust storm is brewing–one of the most important forms of weather on the Red Planet.

Sunspots are just a bonus. A recent study shows that Perseverance sees more than 40% of all sunspots despite the fact that Mars is 78 million km farther from the sun than Earth and the rover’s camera doesn’t put many pixels across the solar disk. It is able to resolve about 10% of the biggest sunspots into multiple pixels.

Perseverance has one big advantage. It can see parts of the sun we cannot. From where Mars is currently located, Perseverance views more than half the sun’s farside, giving it a preview of sunspots still hidden from Earth. That’s how the rover spotted AR3363 days in advance.

People on Earth saw the sunspot for the first time on July 5th:

“A very big sunspot is coming!” says photographer Philippe Tosi of Nîmes, France, who inserted an image of Earth for scale.

Just don’t forget, Perseverance saw it first. Daily photos from Perseverance are available here. Select the date and camera (MASTCAM-Z), then start looking for sunspots.

more images: from Philip Smith of Manorville, New York; from P-M Hedén of Vallentuna Sweden; from Sylvain Weiller of Jerusalem, Israel