BAN #323: Citizen science panel, Spectacular Martian dunes

17 May 2021   Issue #323

[The planetary nebula M 2-9, winds from a dying star. Credit: NASA / ESA / Hubble Legacy Archive / Judy Schmidt]

Subscribers, one grain at a time, move mountains

Upcoming Appearances/Shameless Self-Promotion

Where I’ll be doing things you can watch and listen to or read about

This coming Friday and Saturday (May 21/22, 2021) SciStarter is holding an informal online conference highlighting citizen science projects, something near and dear to my heart — where non-professional-scientists (that very likely means you) can participate in actual scientific experiments by analyzing real scientific data.

NASA is a partner in this, and I am chuffed to let you know I will be moderating a panel called “Planet Palooza”, featuring citizen science projects involving finding and characterizing exoplanets, alien worlds orbiting alien stars!

The panelists are project scientists from groups including Backyard Worlds, Disk Detectives, Planet Patrol, and Planet Hunters

My panel will be on Friday, May 21, 2021 at 3:00 p.m. Eastern (US) time (19:00 UTC)

Register for it here!

The beauty of SciStarter is that it’s a one-stop shop for all these projects; you can sign up for them individually but SciStarter is a way to keep track of what you’re doing across all the different platforms.

Citizen scientists have found asteroids in Hubble images, a new kind of aurora on Earth, mapped galaxy spiral arms (which has led to an intriguing discovery), and don’t forget it was citizen scientists who found Boyajian’s Star!

So please join me for the panel. We’ll be taking questions from viewers, too. And join up with SciStarter to start your hunt! Who knows: You may find your very own actual exoplanet.

Blog Jam

What I’ve recently written on the blog, ICYMI

[Jupiter in the infrared from the Gemini Observatory. From Wednesday’s article. Credit: International Gemini Observatory/NOIRLab/NSF/AURA, M.H. Wong (UC Berkeley) et al. Acknowledgments: M. Zamani]

Monday 10 May, 2021: More evidence that Mars is volcanically active right now. Today.

Tuesday 11 May, 2021: Supermassive stars might be born in the chaos around supermassive black holes

Wednesday 12 May, 2021: New pix of Jupiter will rock your (very very large) world

Thursday 13 May, 2021: What created this enormous spiral in the Martian north pole? Wind. And Time.

Friday 14 May, 2021: The eerie, unearthly sight of polar stratospheric clouds

Pic o’ the Letter

A cool or lovely or mind-bending astronomical image/video with a short description so you can grok it

I have conflicting images of Mars in my head.

And by images I mean “how I think of it when I think of it”, like what overall properties pre-exist on my brain when I ponder Mars.

One of them is the Dead Planet: Dry, cold, nearly airless, frozen in time, inhospitable, and, to be frank, bleak.

Then there’s this:

[Sand dunes in a crater on Mars. Credit: NASA/JPL/University of Arizona]

Gorgeous. Those are sand dunes in an unnamed 5-kilometer-wide crater on Mars (the image is roughly 1 km across)

Mars is covered in basaltic rock, igneous rock from volcanoes. Over time this erodes into small grains that can be blown around by the wind, though the air on Mars is so thin it takes a long time accumulate into a dune. Dunes themselves move as sand on the upwind side gets blown over or around the dune and deposited on the leeward side (that link goes to an extremely cool animation of a dune moving over time). Over time this process effectively moves the entire dune downwind.

Basaltic grains are heavy (compared to the extremely fine-grained dust which is mostly forms of iron oxide — ruse — that covers everything on Mars and gives it its red-orange color). Once they fall into a crater it’s hard for the wind to blow them out, so it’s common to see dune fields at the bottoms of craters.

This color image (using red, green, and blue filters, so relatively true color) shows a part of the dune filed in this small high-latitude crater, and you can see the dark basaltic material covered in reddish dust, as well as bright parts around the peaks due to frost.

[Context view of crater on Mars with dunes. Credit: NASA/JPL/University of Arizona]

A wider shot shows the whole crater (though not in color) and you can see some dunes near the bottom are separate from the field. One of them on the left is sitting in a gully down the crater wall, which isn’t surprising; grains may settle there and the wind has an even harder time blowing them out.

The crater wall itself on the right has long streaks in it that may be due to water ice forming there and sublimating (turning into a gas) in the spring. You can see lots of wide gullies around the wall that are caused by something dislodging material in the wall which then slides down to the floor. There may be more than one thing that causes these gullies, including dry ice or water sublimating. They tend to change with the seasons, so it’s clearly linked with temperature. There are also dark streaks in some crater walls called recurring slope lineae which have a similar origin.

And all this reminds me that the first image I have of Mars may indeed be true, but is short-sighted without taking a longer view. The second image I have of it is more fair:

Dynamic, active, changing, colorful, intriguing, awe-inspiring.


I think I prefer the second view.

Follow NASA’s HiRISE camera images of Mars on Instagram and Twitter. Trust me: You won’t regret it.

Et alia

You can email me at (though replies can take a while), and all my social media outlets are gathered together at Also, if you don’t already, please subscribe to this newsletter! And feel free to tell a friend or nine, too. Thanks!