Bad Astronomy
The entire universe in blog form

Dec. 8 2016 4:53 PM

John Glenn, the First American to Orbit the Earth, Has Died at 95

John Glenn has died. The cause of death has not been announced, but he was hospitalized at the Ohio State University Wexner Medical Center a week ago, reportedly in declining health. He was 95.

To call him an American hero is understating the case. He was a military aviator, signing up after the bombing of Pearl Harbor in 1941. He was a test pilot after that, and was also a U.S. senator from Ohio for 25 years, from 1974 to 1999.


But of course he is best known as an astronaut. He was in the first group of astronauts chosen by NASA, called the Original Group or, more popularly, the Mercury 7. He was also the first American to orbit the Earth, circling our planet three times on Feb. 20, 1962, in a Mercury capsule named Friendship 7. This was at the height of the Cold War and space race with the Soviet Union, and was a major step in the U.S. goal of putting humans on the Moon.

Friendship 7 is on display at the Smithsonian’s Air and Space Museum in Washington, D.C., and I highly recommend visiting it. It’s tiny—the size of a very small car. Yet Glenn stepped into it when it was mounted on the top of an Atlas rocket and rode that nickel/aluminum/fiberglass can into space. The bravery of an act like that is staggering, especially given how early on it was in our attempts to explore space.

But after splashdown his career as an astronaut wasn’t over: He flew again into orbit in 1998 on the Space Shuttle Discovery, making him, at the age of 77, the oldest human to fly. He lobbied hard to go and was chosen as a payload specialist by NASA. That decision was controversial; many people inside and outside NASA said that he was not “mission essential” and that his flight was political payback. Glenn himself disagreed, saying he trained hard for the flight and was qualified as a specialist. He also pointed out that there were geriatric studies that could be done on him to see what the effects of microgravity were and quite a few medical experiments were performed on him during the flight.

It’s interesting to note that Glenn holds another record as well: the longest gap in time between two spaceflights for any human. Given that it was 36 years, that record may stand for some time.

We’re at a time now when our first astronauts are mostly gone; Glenn was the last living member of the Mercury 7, and only seven of the Apollo Moonwalkers are still alive today as well. Even when recognizing and mourning his passing, I can’t help but think that we are at a cusp in our exploration of space, standing at the threshold of a huge leap forward in our ability to put humans into space. More countries than ever are building their own space programs with an eye toward crewed flights, and even private companies are working hard and making giant leaps in that direction. We’ve had people living continuously on board the International Space Station for more than 16 years now.

We have John Glenn to thank for much of this. He was one of the pioneers, one of the first humans in all of history to leave behind the Earth, even if only for a few hours. With all of his monumental accomplishments in his lifetime, my hope is that the one he will be remember forever for is this: He helped set in motion the greatest journey humanity has ever taken, a journey that, hopefully, will never end.

Dec. 8 2016 9:00 AM

An Island of Stars in a Sea of Stars

I find some astronomical objects curious not so much in and of themselves, but also because of where they’re located.

Take M11, also called the Wild Duck Cluster. It’s about 6,000 light years away, and it’s an open (or galactic) cluster consists of about 3,000 stars. The cluster is something over 200 million years old, making it middle-aged; after a billion years or so such clusters dissipate as their stars interact gravitationally, ejecting members ones after another.

Dec. 7 2016 9:00 AM

The Universe Voids Itself, and Einstein Predicted It

Most of the Universe is empty space.

Duh. I mean, sure, that’s why we call it space. But what’s so very interesting about this is what you see when you look on very large scales; scales so huge that galaxies become mere dots. You might expect matter to be strewn evenly throughout the Universe, but it isn’t. Over these vast vistas, matter in the Universe is clumped, falling along huge filaments and sheets. These in turn are curved, closing in on themselves.


The Universe is foamy! It looks like a sponge, with matter clumping along the outside of the bubbles. Shortly after the Universe formed, dark matter clumped up, creating those filaments. These acted like gravitational scaffolding, its gravity attracting normal matter, which then fell onto the filaments like Spanish moss hanging from tree branches. This material formed galaxies and clusters of galaxies.

Matter is still falling into those filaments today. As it does, the voids—the bubbles of the sponge—get bigger. We can predict how they grow using Einstein’s Theory of Relativity, which describes how the Universe expands and how the matter and energy in it behave as it does. This video from the Max Planck Institute for Astrophysics shows that growth in a computer simulation:

But there’s more to this: Dark energy, the weird stuff pervading space that’s causing the Universe to expand faster every day, is also in there, inflating the voids. Relativity, as originally formulated, doesn’t include that. If we can measure just how voids grow we can use that as a test of relativity and also understand better how these gigantic pockets of nothing get bigger. To do this, traditionally, astronomer measure that growth by examining the galaxies along the bubble edges.

But that turns out to be hard, because galaxies aren’t just falling onto the filaments. They also have what’s called peculiar motion, sideways velocity which makes measuring their precise velocity difficult. What to do?

A group of astronomers did something clever: Instead of looking at the galaxies, they looked into the voids themselves. Using observational data that shows distances to galaxies in the Universe—and therefore the locations of voids—they compare how these voids change in shape over time to what’s expected by computer models using relativistic calculations.

Not surprisingly, they find relativity to be pretty robust. The behavior of the Universe appears to obey the rules laid down by relativity, which is reassuring. I’ll note relativity has been tested approximately a bazillion times, and always comes up looking good.

So while that’s not exactly shocking, what I find interesting about this is that by looking at the voids instead of the galaxies around them, the astronomers who did this work were able to improve on previous methods dramatically, with uncertainties (that is, statistical accuracies) four times smaller than previous models!

That’s pretty dang good. We’re still learning just how the Universe behaves on the very largest scaled; heck, dark energy was only discovered in 1998! Research like this will help us understand what the Universe itself is doing as it ages and grows, and that to me is simply stunning. Even if you don’t understand the details of the work or the math behind it, know this: Astronomers are trying to understand literally everything, across all space and time.

And they’re doing a pretty good job of it.

Dec. 6 2016 9:00 AM

An Irregular Mystery

Galaxies are massive collections of stars, gas, and dust (and dark matter, too). They come in four basic shapes: spiral (like our Milky Way), elliptical, peculiar, and irregular.

Irregulars are pretty much like the name says: They tend not to have an overall structured shape, but are, well, irregular. Still, despite that, some do have a semblance of shape, and it’s not always clear why.


Take IC 3583, for example. That’s the galaxy above, in a gorgeous Hubble Space Telescope image. It’s definitely irregular, but not quite. It appears to have a bar running across it, a thick rectangular structure. Many galaxies have bars (the Milky Way does across its core), even some irregulars. Usually they form from the weird way gravity works in galaxies; instead a single massive object in the center like the Sun anchoring the solar system, the mass of the galaxy is spread out, and that can cause odd structures to form like spiral arms and bars.

It’s possible a bar like that could get its start if the galaxy interacted with another one; the gravity from a bigger galaxy can pull on the smaller one and distort it, causing matter to move around and form bars like that.

As it happens, IC 3583 sits very near a much larger galaxy, the spiral M 90—which itself looks weird; it has long streamers coming out of it as if it recently encountered another galaxy.

Aha! So is that it? These two had a cosmic tryst, both leaving the encounter a little shaken?

Not so fast. They appear to be close in the sky, but are they close together in space? Two objects can appear to be next to each other but at vastly different distances—like looking out your window past a tree in your yard to the mountains kilometers away. So it’s a legitimate question to ask if IC 3583 and M 90 are actually physically close to each other.

And the answer is … we don’t know. One way to get the distance to a nearby galaxy is to look at some of its brightest stars. We know how much light those stars give off, so by measuring their apparent brightness, we can get a distance to the galaxy.

And that’s where this gets weirder. M 90 is a member of the Virgo Cluster, a nearby and decently large group of galaxies. We’re pretty sure M 90 is a member, and that puts it about 60 million light-years away.

But looking at the stars in IC 3583 indicates it’s only a little more than 30 million light-years away, well in the foreground of Virgo. If that’s the case, the two galaxies are unrelated, despite appearances.

But wait! I said M 90 looks weird too; how can that be then? It turns out that galaxies like M 90 can be moving through the cluster rapidly, and the gas that exists between the galaxies can strip off the gas inside of rapidly moving galaxies. It’s like being in a car when your dog decides to, um, make a foul odor, so you open the windows, letting the air blow through the car, stripping away the mixture of methane, hydrogen sulfide, and mercaptans.

So M 90 may be odd looking because it’s ramming through the cluster, and IC 3583 may look odd because sometimes irregulars are just odd looking. Coincidence.

I know that’s not an entirely satisfactory answer, but here we are. Galaxies, even nearby ones, are still quintillions of kilometers away, and that’s a long haul. It can be difficult to know everything about them … but then, that’s why we study them! We know way more about them than we did a century ago, but that doesn’t mean our knowledge is complete.

Science is a journey. There may not be a single, vivid end to that journey, though it tends to steer toward the path of reality. The fun part is the learning, of solving mysteries along the way. We may never finish—I certainly hope not!—but there’s a lot to see and do along the way.

Dec. 5 2016 8:45 AM

Follow-Up: Why the House Science Committee’s Climate Change Denial Is So Wrong

Last week, I wrote about an appalling tweet by the U.S. House of Representatives Committee on Science, Space, and Technology. The committee—currently run by a GOP majority—has a history of outrageous climate change denial, and also has a history of tweeting about it.

But even for them, the tweet from Thursday was outrageous: It linked to a ridiculously bad article by climate change denier James Delingpole, who is known for ramping up the hyperbole to 11 when he writes on global warming. He in turn got his bad data from another noted denier, David Rose, writing for the Daily Mail, the Mos Eisley tavern of anti-reality aficionados.


The claim made by Rose is simple: Temperatures since February 2016 have plummeted by a full degree Celsius in more recent months, casting doubt on the reality of global warming.

As I pointed out in my own article (and with far greater detail given by Tamino at the blog Open Mind), Rose’s claim is completely wrong. He cherry-picked data so severely that they’re essentially meaningless; the equivalent of flipping a coin once, having it come up heads, and then declaring it always comes up heads.

He looked at patchy data with high uncertainty from a very short time period and tries to make conclusions about it. What he (and in turn Delingpole and then the House Committee on Science) ignored was the trend. These shenanigans have been graphically debunked by climatologist Gavin Schmidt, who is the director of the NASA Goddard Institute for Space Studies, and is a noted expert in climate change.

Temperature trend
This is what the deniers don't want you to see: the trend.

Dr. Gavin Schmidt, used by permission

To create this animation, Schmidt used land surface temperatures from GISTEMP, which is measured using a variety of methods including meteorological stations. He shows that yes, there is a large drop from earlier this year to October, due in part to El Niño subsiding. If all you see is the first frame of this animation, you might suppose something really is weird!

But there’s more. The second frame shows the same measurements going back much further in time, to 1970. The y-axis is what’s called the “temperature anomaly,” the deviation from some average (in this case, the temperatures from 1951 to 1980; if the anomaly is 0, then you’re right on average, if it’s a degree above average it’s shown as +1, and so on). As you can see, once you look back more than a few months or even years, there is a clear upward trend to the temperatures.

The third frame overplots the average temperature for each year in red, making the trend more clear (the dashed line is an estimate for the rest of 2016 using previous years as a guide). The fourth frame corrects those averages for El Niño (the technical name is El Niño-Southern Oscillation, or ENSO); it’s actually not a huge correction, and again the trend is clear.

The fifth frame shows a mathematical fit to the data to just show the trend, and as you can see it’s heading up.

The other thing to notice here is that we see lots of very short-term fluctuations, some swinging more than a degree over small periods. But that’s not surprising! The shorter the time, the more you expect the temperature to move; the average daily temperatures over a week can be all over the place, but the annual average temperatures should be relatively stable from year to year.

Yet, despite that, the trend is obvious: The world is heating up.

This is precisely why we say Rose was cherry-picking. Whatever his motivations, he only showed a very limited slice of what’s really going on, and in that way hid reality from everyone who didn’t know to look deeper.

Or who didn’t want to look deeper. As I’ve written before, the science is the science, but the inconvenient truth about global warming is that it goes against a lot of political ideology, especially when that ideology is fueled by money from the oil industry.

And without a doubt that’s why the House Science Committee took to Twitter; it wanted to advance its dogma, truth be damned. It is not interested in actual science, or in reality. It is only interested in its agenda, and that agenda is to further the cause of fossil fuel, even if it means setting the world on fire.

Dec. 2 2016 8:45 AM

The House (Anti-)Science Committee Strikes Again

The House Committee on Science, Space, and Technology is, ironically but shocking to no one who understands the majority party, quite anti-science. For years now, the committee and its chairman, Lamar Smith, R-Texas, have been merciless in their attacks on both climate scientists and the National Oceanic and Atmospheric Administration. Smith—who receives a large amount of funding from fossil fuel interests—has been subpoenaing NOAA staff and data repeatedly in what is a transparent attempt both to create a chilling effect and to directly prevent them from doing their very important research into human-generated global warming.

The committee's Twitter account often reflects this ideology. And Thursday afternoon, to the dismay of many, they tweeted a climate-denying “news” story from Breitbart.


Yes, that Breitbart, the racist, misogynistic über-right-wing site that calls itself a voice for the “alt-right” movement, which is—as my Slate colleague Jeremy Stahl says—composed of “neo-Nazis in suits and ties.”

The content of this tweet is the same sort of thing you’d get if you fed a bull 20 kilos of Ex-Lax and stood behind it for a while. Global warming, of course, is real. The Breitbart article in question is written by James Delingpole, a flat-out climate change denier who has a history of writing grossly misleading articles about global warming. He gets this information from yet another climate change denier, David Rose, who wrote an article for the execrable Daily Mail claiming that global temperatures have dropped by an entire degree Celsius since this summer. Contrary to what the Daily Mail might have to say, global temperature is indeed increasing.

In a nutshell, Rose is guilty of extreme cherry-picking. He looked at a single temperature data set from a specific layer of the Earth’s atmosphere and only used measurements over land. And to make matters worse, he only used data going back to 1998, a big no-no: That year was unusually warm, so starting there falsely makes it look like temperatures haven’t risen much.

He also is chasing local fluctuations and ignoring the decadeslong trend. And that trend is up. The Earth is heating up. If you want more details, Tamino at Open Mind debunks Rose’s claims quite thoroughly.

As wrongheaded as it is, this kind of climate denialism is de rigeur for people whose stance is so anti-science. I’m used to it, awful as it is. But it’s the fact that the house committee linked to Breitbart that’s so disturbing.

And this isn’t even the first time this Twitter account has linked to a Breitbart article. It did so on Sept. 8:

And then, after finding all this out, I found (via Karen James) that Committee Chairman Smith actually has written for Breitbart! As physicist Robert McNees points out, this has been going on for some time now.

And mind you, all this was before Trump was voted into office. These tweets, and the information they cite, are a scary reminder that climate deniers will feel emboldened by Trump’s election. Trump’s team is already planning to cut global warming research at NASA. As winter approaches, we’ll likely see more reality-challenged senators bring in snowballs to the floors of Congress and say, “What global warming?” every time a cold snap arrives, even though a lot of the brutal “polar vortex” conditions are actually tied to the effects global warming.

The good news is some in Congress do recognize the reality and the importance of climate change. Rep. Don Beyer, D-Va.*, for example, who tweeted:

Good on him! We need more people like him in Congress willing to speak up against this sort of denialism.

The stakes here are as high as they can get. Climate denialism by Breitbart now gets the imprimatur of the federal government. This cannot stand. Act accordingly.

P.S. If you want to contact the committee directly about this, its phone number is 202-225-6371. If you do, be brief, and be polite! If you have a representative on the committee, mention that as well.

Correction, Dec. 2, 2016: I originally wrote that Don Beyer was a representative for Maryland. He's from Virginia.

Dec. 1 2016 1:58 PM

Russian Resupply Rocket Lost During Launch

News is still coming in right now, but it looks like a Progress capsule loaded with supplies for the astronauts on the International Space Station was lost as it was heading up into space this morning. It was uncrewed, so there was no loss of human life.

Jason Davis at The Planetary Society has details, and you can also get more at SpaceFlightNow. The launch started off well, but the third stage cut off prematurely. Contact was lost a little over six minutes after liftoff, and Roscosmos, the Russian space agency, has confirmed the loss of the vehicle 190 kilometers over the Tuva mountains in south central Russia; the Progress capsule lost altitude and burned up in the atmosphere. There are unconfirmed reports of debris in the remote area as well though no injuries reported.


The good news is that the ISS is well stocked, and a Japanese supply ship is due to launch in a week or so, so the astronauts are in no danger.

I’m keeping my ears open for more news; it’s unclear how this will affect future Russian launches, including astronauts to ISS. I’ll note SpaceX just announced their return to flight mission for a Falcon 9 on Dec. 16; this will be their first launch since the pre-launch explosion of a Falcon 9 during fueling on Sep. 1, 2016. That’s good news, as they have several resupply missions planned to ISS as well.

More info will be added here as I hear and confirm it.

Dec. 1 2016 9:00 AM

How the Moon Got Its Weird

Our Moon is really weird.

I mean that literally. It has a lot of physical qualities that are pretty hard to explain. For example: It’s big, fully a quarter the diameter of the Earth. Excluding Pluto and Charon, it’s the highest known ratio of moon to parent body size for any large object in the solar system.


There’s more. All other moons in the solar system orbit over their parent planet’s equator. Our Moon’s orbit is tipped by much more; it actually is tipped 5° to the Earth's orbital plane around the Sun; the Earth itself is tipped by 23° to that.* Also weirdly, while there are some differences, overall its composition is similar to Earth’s. That’s unusual too; most moons are way different than their planets.

A lot of these problems with our Moon were solved when the Giant Impact hypothesis was proposed. Early on in the solar system, a disk of material orbited the Sun, and it was from this disk the planets formed. Small bodies condensed out of it, collided, and grew to become the planets. At some point, tens of millions of years after it initially formed, the Earth was whacked by a Mars-size object at a glancing angle. This flung a huge amount of material into space, which formed a disk over Earth’s equator. The Moon coalesced from this ejecta, and the Earth was left spinning rapidly, with a day just five hours long. Over time, interactions between the Earth and Moon slowed our spin and moved the Moon out, away from the Earth to where we see it now.

That explains a lot of the weirdness we see from the Moon; its unusual size is due to the large amount of material blasted into space, for example. But there are problems. If the Moon formed over the equator, why is its orbit tipped by so much now? Also, in the impact models, the Moon should have a lot of material from the impactor, but instead is closer to an Earth-like composition. Why?

A group of scientists think they may have found the answer. And as a bonus, it explains yet another odd thing: Why the Earth is tilted by 23° to its orbit.

Earth tilt
Can the Moon explain why the Earth's tilt with respect to its orbital place (also called its obliquity) is so large? Maybe.

Dennis Nilsson

What they propose is a modification to the giant impact idea. In their model, they have a much more energetic impact. The tremendous power of the collision set the Earth spinning with a two-hour day, faster than in the classic impact hypothesis. The higher energy also meant the material ejected mixed a lot more, so that both the Earth and Moon wound up with similar compositions.

Then comes the really strange part. You know how a kid on a swing can make their arc go higher by pumping their legs? By doing that they transfer the energy of their legs’ motion into the swing. But they have to time it right to make it work, doing it at just the right time in the arc. When two cycles line up like this it’s a called a resonance, and it’s a huge influence on the motions of moons and other bodies.

After the Moon formed, it started moving away from the Earth due to the complicated dance of gravity and tides. I explain how this works in Crash Course Astronomy: Tides, if you want the details. The outcome of this is that the Moon’s orbit slowly expanded and the Earth’s spin slowed.

In the new model though, there’s a twist: The giant impact torqued the Earth hard, so much so that our planet’s pole was aimed more toward the Sun than it is now. This changes that tidal evolution of the Moon. As it moved away it went through a series of resonances, some connecting the way it moved away from Earth with the Earth’s motion around the Sun (like the way a kid’s legs connect with the swing’s motion).

What the scientists found in their models is that this affected both the tilt of the Moon’s orbit as well as the tilt of the Earth itself. As the Moon’s orbit expanded, it also moved around, changing its orientation. The Moon’s tides tugged on the Earth all that time, eventually yanking the Earth closer to being upright (the Earth’s orbit was unaffected, though).

In the end, the Moon settled into its current orbit, tipped 5° to the Earth's orbital plane, and the planet stayed at its 23° tilt to its orbit around the Sun. This video shows the effects graphically:

The Sun is off to the left, and the Earth’s axis points near it. As time goes on (starting less than a million years after the impact) the Moon’s orbit changes in orientation, tilt, and shape, and the Earth’s axis changes, too.

I’ve left out a lot of details because they’re complicated and would take a lot to explain (feel free to read the paper, but there’s a lot to it). Still, this is the meat of it. The big question is: Is this what actually happened 4.5 billion years or so ago?

That’s a different question. Just because this new idea explains more stuff we see now doesn’t make it right. Lots of other ideas have come along, and no doubt more will. Perhaps this idea is correct, and still needs modification (for example, we know a lot of things happened after the Moon formed; its far side and near side are really different, and more hypotheses have been proposed to explain that). Maybe something better will come along that explains even more.

But that’s science! For a long time—centuries, millennia—we had no more than guesses on how the Moon formed. As we studied it more we learned more about it, and were able to cull a few hypotheses. Then we went there and got samples, pieces of the Moon we could study in the lab. More mysteries surfaced, and the giant impact idea explained a lot of them. But it’s been modified, over and again, tweaked here and there, and now we may very well be closing in on the complete history of how our gigantic satellite came to be.

There are a lot of reasons I love science, but one of them is that it doesn’t flinch from telling the big stories, and welcomes changes to make the story better.

*Correction, Dec. 1, 2016: I originally wrote that the Moon is tipped 5° to the Earth's equator, not the Earth's orbital plane.

Nov. 30 2016 9:00 AM

Another Jumping Sun Dog

Just recently I wrote about one of the coolest and weirdest weather/optical phenomena I’ve ever seen: crown flashes, also called jumping sun dogs. They’re streamers of light above storm clouds that appear to dance and flash, sometimes quite rapidly, looking like search lights or huge light sabers.

They’re almost certainly caused by long ice crystals above the cloud that align themselves with the cloud’s electric field. If you see them from the right angle, they bend (or refract) the sunlight toward you, causing the glow. When lightning erupts from the cloud to the ground (or inside the cloud) the electric field changes radically, realigning the ice crystals. When this happens they suddenly bend sunlight in a different direction, causing the glow to shift.


By coincidence, a BA reader named Mikhail Chubarets sent me an email a few months back (before I wrote the article linked above), letting me know about an amazing video of a crown flash, but I missed his email! I was going through some old ones and spotted it, so now I get to share this short but way cool video with you:

The video was taken in Zvenigorod, a city in Moscow Oblast in Russia, on July 3, 2016. It really shows a lot of detail, and I gasped out loud at the 1:25 mark when it shows the glow sweeping rapidly like the blade of a sword into a new position.

I have some mixed feelings about this, to be honest: While this is one of the most astonishing optical phenomena I’ve ever seen, the things is, I’ve never seen one for myself. I recently was able to scratch Kelvin-Helmholtz clouds off my “to see” list, as well as (yikes) a tornado. But this? Crown flashes are pretty rare; besides having the ice crystals aligning correctly you also have to be in the right spot for the geometry to line up, otherwise the sunlight isn’t bent your way. They’re rare enough that I hadn’t even heard of them until a couple of years ago.

It seems unlikely I’ll ever witness one. Ah well. I can add that to a long list of things still to witness (like a total solar eclipse, a full-blown aurora, a display of undulatus asperatus, and more). I do get around, and I do tend to look up, so I can still hope. There are a lot of truly wonderful things to experience on this planet of ours.

Nov. 29 2016 9:00 AM

A (Frozen) Great Lake of Water Is Found Beneath the Surface of Mars

Mars has long been a target of human curiosity. A blood-red eye in the sky, hanging, baleful. Our understanding of it has changed over time; it was thought to be somewhat Earth-like for a while, but then we sent space probes there and found it to be a desiccated, dead world.

Well, at least for now. We have pretty conclusive evidence it once had plentiful liquid water on the surface, including lakes, rivers, and even oceans. That was eons ago; the solar wind stripped away the atmosphere from Mars, and the water mostly boiled away with the air.


Mostly. We’ve known for a long time there’s lots of water ice on the planet; both poles have water ice caps on them several kilometers thick (in turn capped by seasonal layers of frozen carbon dioxide —dry ice— a few meters thick). You kinda expect that at the poles. But there’s also evidence for water just under the surface at mid-latitudes: Small impacts from asteroids have excavated ice that can be directly seen. These are wee craters, so it’s not clear just how much ice there is down there.

But now scientists using a radar mapper on board the Mars Reconnaissance Orbiter (or MRO) have found more water ice at these lower latitudes, and a lot of it: The volume is enough to fill Lake Superior, the largest of the Great Lakes in North America.

Yeah, that’s a lot of ice.

ice field
Map of the ice field location. The shade of violet represents depth; dark is where the ice is 170 meters thick, and pale where it's about 10.

NASA/JPL-Caltech/Univ. of Rome/ASI/PSI

It’s located in a region called Utopia Planitia (Trek fans will recognize this as the location of the Starfleet Yards where the Enterprise-D was built), at a latitude of 45° north, so quite literally at mid-latitudes. While it’s only a tiny fraction of the total water ice known to exist on (or under) Mars, it doubles the amount known at these latitudes.

It was found using a radar mapper on MRO. Called SHARAD, it sends pings of radar down to the surface, which are reflected back up to the satellite and recorded. Different substances reflect radar differently; the rocks on the surface aren’t particularly good at it, which is why the radar can penetrate the ground. Water, on the other hand, reflects radar quite well, so SHARAD can detect water ice down to a depth of a kilometer below the Martian surface.

Scientists focused their attention on a region in Utopia Planitia that features lots of odd, scalloped terrain (aresain?), which is similar to places on Earth in the Arctic that have underground ice. Combining the data from over 600 MRO passes indicates how much ice there is. The area of the ice deposit is over 300,000 square kilometers and the thickness ranges from 80 to 170 meters. So yeah, that’s a goodly supply of ice.

radar map of ice
A sample of the radar map in one location, showing the location of the bottom of the ice layer.

NASA/JPL-Caltech/Univ. of Rome/ASI/PSI

This is pretty good news for future exploration and colonization plans. Ice is critical for Martian living; it can be melted to drink, broken into oxygen and hydrogen for air and rocket fuel, and can protect inhabitants from solar storms (on Earth our air does this, but Martian air is less than one percent as thick as ours; ice does an excellent job of absorbing radiation).

One last thing: How did the ice get there? One idea is that Mars’ axial tilt varies wildly over time. When it flips, the poles become much closer to the previous equator. The ice sublimates, turning into a gas, which then recondenses in other locations. It can mix with dust and snow out in the mid-latitudes, eventually getting buried.

That’s amazing. An entire planet flipping over like that! It’s hard to imagine what chaos that would wreak on the climate, even for a planet with so little air. Happily, our Moon provides stabilization against this kind of event; it torques the Earth’s axis and prevents it from making big excursions.

Mars is weird. But that’s good! Studying it helps us put the Earth in context with the other planets, and in turn helps us understand our own planet. And that’s good, because we live here.