Suddenly, A Dark Streak Appears on Mars

Oct. 25, 2020: On Friday night, Oct. 22nd, longtime Mars photographer Maximilian Teodorescu of Magurele, Romania, looked at the Red Planet and noticed something he hadn’t seen before. “There is a dark streak in the Tharsis volcanic plateau,” he says. The mystery smudge is circled in these two images separated by about 40 minutes:

“The feature was not visible just a few nights ago when I photographed the same region,” says Teodorescu, who offers an Oct. 19th image for comparison. “Now, I have seen it two nights in a row (Oct. 22nd and 23rd), and other observers have seen it, too.”

What is it? Teodorescu’s first thought was “it must be some kind of cloud or streamer of dust.” Indeed, it is located in the same general area where a long icy cloud sometimes forms when wind whips around the summit of Arsia Mons, an extinct volcano.

To investigate further, Teodorescu projected the streak down onto a Mars Orbiter image of the region:

“The streak is about 600 km long,” he says. “It is close to Arsia Mons, but not a perfect match. Perhaps it is a shadow of the volcano’s ice cloud projected down onto lower Tharsis clouds.”

Mars photographers everywhere are encouraged to keep an eye out for this dark feature whenever the Tharsis volcanoes are facing Earth. Report your observations here, and we will share them.

Realtime Mars Photo Gallery

Rare Red Auroras

Oct. 13, 2020: Arctic photographer Rayann Elzein sees auroras all the time over Utsjoki, Finland. But the auroras he saw last night were different. “They were red,” he says. “Almost only red.”

“Rarely have I seen anything like this before,” says Elzein. “I double-checked the white balance on my camera to make sure nothing was wrong. But it was the same color temperature as on all my other northern lights pictures.”

“Later, we were treated to the usual swirls of green and even some pink nitrogen fringe,” he says. “When the green swirls calmed down, the red returned.”

Auroras are normally green–the verdant glow of oxygen atoms about 150 km above Earth’s surface. Rare red auroras are also caused by oxygen atoms, but at higher altitudes between 150 km and 500 km. At those heights, the temperature and density of the atmosphere favors atomic transitions that emit red photons. Indeed, Elzein’s photos show red stacked on top of green just as theory predicts.

For some reason, unknown to us, the solar wind on Oct. 12th excited oxygen at higher altitudes than usual, giving rare red auroras their chance to shine. Aurora alerts: SMS Text.