In partnership with

The thin red line of Mars’ atmosphere, from Viking

This week I came across this old image of Mars, taken by the orbiter that delivered the Viking 1 lander to Mars in 1976:

This stopped me in my tracks when I saw it. Seeing the clarity of the Martian terrain with the thin, wispy atmosphere visible above it, you could easily imagine being there in orbit looking down on the planet. When I posted this to Bluesky some people questioned whether it was real. It certainly looks unreal, and it’s odd that I’ve never seen it before, so what’s the deal?

It is a genuine photo from the Viking mission, but the caveat is that the original image is in greyscale, taken through a red colour filter. Here’s the original from the NASA website:

That’s no less amazing – the atmosphere and terrain are just as clear. At some point someone has taken this image, cleaned it up and adjusted it to be red rather than grey. So I would say the photo is “real” in the sense that it’s a representation of real data collected by real instruments. But is it accurate? Would Mars look like this if you were in orbit looking directly at it? Unfortunately, no, I don’t think it would.

Your eyes would see a much wider range of colours. So what would you see? Probably something more like this, from the Hope Orbiter, taken with multiple (RGB) filters:

That’s amazing, too.

Science Stories You Can’t Get Anywhere Else

Feed your curiosity with Nautilus — a science newsletter for thinkers, seekers, and the endlessly curious. Each week, we bring you beautifully written stories at the intersection of science, philosophy, and culture. From the physics of time to the psychology of awe, our essays, interviews, and ideas dive beneath the surface and linger in the mind.

Join a global community of readers who believe that big questions deserve thoughtful answers. Whether you're a lifelong learner or just love a good mystery of the universe, Nautilus will challenge how you see the world — and maybe even yourself.

Sign up now and start thinking deeper.

Sign up today

Three Alpha is a free weekly newsletter. Not subscribed yet? Make sure you don’t miss future editions by subscribing now!

You can support my work and help ensure I can keep writing by upgrading to a paid subscription or sending a one-time payment.

Solar System

• Mars has a magnetic field that is stronger in the southern hemisphere. New research suggests this could be caused by Mars having a fully liquid core (unlike Earth which has a solid core surrounded by liquid) which cooled more rapidly on one side than the other. [Universe Today, Earth.com, Discover Magazine]

• Carbon-rich meteorites often lack evidence for collisions which are present in other types of rock, because the impacts themselves release gasses which blast away the evidence. [Space.com, Science Daily]

• Three NASA cubesats, dubbed EZIE, have started their mission to study the auroral electrojets – large, high altitude electric currents in the Earth’s ionosphere. [Space.com, Phys.org]

Galaxy

• A gravitational microlensing survey suggests there are loads of “super Earths” (large, rocky planets) in wide orbits around their stars, at a similar distance to Jupiter and Saturn. [Ars Technica]

• An analysis of archived X-ray and radio observations has shown that the jets created by accreting black holes are launched when the accretion disk shrinks and reaches the innermost stable circular orbit (ISCO). [Science Daily]

• New papers find multiple ways dimethyl sulfide (DMS) can be produced without life and question whether DMS was even detected on K2-18b, casting doubt on recent claims of the detection of life. [Universe Today, Space.com, NPR]

• The “exoALMA” project has used the ALMA radio telescope array to produce amazing images protoplanetary disks – new planets forming around young stars. [ALMA Observatory, Popular Science]

Finally

Testing of the Vera Rubin Observatory is continuing. Check out this video of the colour filters being changed (the observatory will take images with six different filters, using two different filters each night):

What is Three Alpha? Other than being the name of the newsletter you’re reading now, the name “three alpha” comes from the triple-alpha process, a nuclear chain reaction in stars which turns helium into carbon. Read more here.

Who writes this? My name is Dr. Adam McMaster. I’m an astronomer in the UK, where I mainly work on finding black holes. You can find me on BlueSky, @adammc.space.

Let me know what you think! You can send comments and feedback by hitting reply or by emailing [email protected].