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SYFY WIRE Bad Astronomy

Your daily Mars forecast: Fatally cold, with some light winds

By Phil Plait
Your weather update, straight from Mars, courtesy NASA’s Mars InSight lander. Credit: NASA/JPL-Caltech

When I got up this morning, it was about -11° C outside with a weak breeze blowing a very light snow. It was a typical Colorado winter dawn, and before I went out to feed the animals I donned multiple layers, thick gloves, and a balaclava to keep my delicate nose from being turned to ice and chafed away.

But I should count myself lucky. What I was experiencing as a low temperature for the day would've been the high on Mars. And on top of everything I wore, I'd also need a heavy oxygen tank and pressure suit, or else my nose freezing solid would've been the least of my worries.

I know this because the NASA Mars InSight lander is now broadcasting daily weather updates!

Your weather update, straight from Mars, courtesy NASA’s Mars InSight lander. Credit: NASA/JPL-Caltech

InSight touched down on the Red Planet on November 26, 2018, in a flat area called Elysium Planitia, near the equator. Its mission is to probe the Martian interior, and it's loaded with instruments to do just that, including a seismometer (that was just deployed on the surface a couple of weeks ago), a thermal probe to see how heat moves through the crust, and various other detectors that will give scientists back here on Earth a good look at what's going on inside Mars.

It can also monitor what’s what on the surface, too. It's equipped with a pair of wind and temperature sensors on its deck, exposed to the Martian environment, as well as an air pressure sensor inside the lander itself.

The locations of the temperature, wind, and air pressure sensors on Mars InSight. Credit: NASA/JPL-Caltech

The data are sent back to Earth, allowing techs at NASA's Jet Propulsion Laboratory to create the Daily Weather Report for Mars, a public site with all the info you need to plan your Martian picnic in Elysium (my advice: don't).

So yes, while the low for me earlier today was in the negative teens, around the same time that was the high for Elysium Planitia. The low there was a soul-freezing -95°C. That's cold enough to freeze carbon dioxide right out of the air! On Mars, it can snow water ice, but also dry ice. Don't catch those flakes on your tongue.

Not that you'd want to open your mouth on Mars. The pressure at InSight's landing spot has been averaging around 720 Pascals — about 0.7% of the air pressure at Earth sea level. That's enough to tear the breath out of your lungs, so you should probably keep your pressure suit sealed up tight. That makes for a crappy picnic, but better than freezing solid after you suffocate.

Landing sites for various NASA Mars missions, including InSight (right), located in Elysium Planitia near the equator. Credit: NASA/JPL-Caltech

In better weather news, at least the wind won't be a problem. The wind speeds around InSight are variable, maxing out around 50 kilometers per hour. In a reverse of the temperature and pressure, that would be terrible picnic weather on Earth — it's a moderate gale — but the low air pressure on Mars reduces that to a barely noticeable whisper. The force you'd feel is reduced by a factor of about 150 due to the thin air: That's enough to pick up some of the very fine-grained rusty dust pervasive to Mars, but it won't blow your picnic blanket away or your napkins into your potato salad*. Still, keep your eyes open for dust devils.

I really like that this weather report is being created for the public. I imagine teachers can use it in the classroom as a project for students; they can learn about Mars, investigate how things change day to day, and even learn how to graph data. There's lots of room for creativity in its uses.

Dressing for the weather on Earth is a little different than for Mars, because this would be considered a warm spring day. The indigenous fauna seem friendly, though. Credit: Phil Plait

Plus it's just cool. As beautiful as Colorado winters are, I know that around the end of February I get a wee bit tired of the season and start looking forward to the equinox. Having the conditions on Mars at my fingertips gives me some perspective, and makes me less likely to grumble at my own local situation


*I hear Mark Watney has a good recipe.


No it won’t.