Tag: planetary science

Green Skies on Mars

~ J.S. Pailly ~ 12 Comments

Hello, friends!  So I learned a new thing about Mars.  Recent research, published just last year in Nature Astronomy, says that the nighttime sky on Mars sometimes glows green.  Super bright green.  Bright enough that this green glow would be visible to the human eye, if any human eyes were on Mars to see it.  According to one source I read, this green Martian airglow would be comparable to “moonlit clouds on Earth.”

So how does this happen?  Chemistry!  During the day, sunlight zaps carbon dioxide (CO2) gas in Mars’s atmosphere, breaking it up into ionized carbon and oxygen atoms.  At night, those ionized oxygen atoms recombine to form molecular oxygen (O2).  This specific reaction—the formation of O2—produces a little light in the green and infrared parts of the spectrum.  (Please note: I have glossed over an enormous amount of detail here.  See the “Want to learn more?” section below for more information).

The infrared glow of O2 formation had been detected previously.  A very faint green glow had also been detected over the dayside of Mars.  The detection of a green glow at night—that is the new discovery!  And also, this green glow is remarkably and astonishingly bright.  Brighter, it seems, than anyone expected.

Which initially made me wonder: if this green airglow on Mars is that bright, how did it go undetected for so long?  But then again, I sometimes overestimate how much we know about Mars.  You’d think we’d know a lot by now.  Mars is the second most thoroughly explored planet in the Solar System, after Earth.  But in truth, we have just barely scratched the Red Planet’s red surface (and we know even less about all the other planets in our Solar System).

So I see this discovery as a reminder: no matter how much we think we know about space, there is still far, far more we need to learn.

WANT TO LEARN MORE?

This discovery was made by the European Space Agency’s ExoMars Mission, currently in orbit around Mars.  Here is a press release from ESA about this discovery.

And here is an article from Universe Today, which goes into more detail about Mars’s airglow, the chemistry behind it, and the way Martian wind patterns and the changing of Martian seasons affect it.

And lastly, for those of you who want to look at the original research, here’s a link to the original research paper from Nature Astronomy (warning: you may encounter a paywall).

Mercury A to Z: Amorphous Ice

~ J.S. Pailly ~ 14 Comments

Hello, friends!  Welcome to my very first post for this year’s A to Z Challenge.  You don’t know what the A to Z Challenge is?  That’s okay.  You can click here if you want to learn more.  My theme for this year’s challenge is the planet Mercury, and in today’s post the letter A is for:

AMORPHOUS ICE

It gets really hot on Mercury.  You probably knew that already.  Mercury is, after all, the planet closest to the Sun.  But it may surprise you to learn that it also gets really cold on Mercury.  Extremely cold.  Like, we’re talking spit-goes-clink levels of cold.

Much like the Moon, Mercury has virtually no atmosphere.  That means there’s no atmospheric convection to transfer heat from the dayside of Mercury to the nightside.  Atmospheres can also act as a sort of blanket to keep a planet’s surface warm during the night.  But again, Mercury has virtually no atmosphere.  No blanket effect.  All the heat Mercury’s surface soaks up during the long Mercurian day is lost during the equally long Mercurian night.  As a result, the nightside of Mercury is one of the absolute coldest places in the entire Solar System.

Now, imagine if there were a place on Mercury where it is always night and never day.  Places like that exist at the bottoms of deep, dark craters clustered around Mercury’s north and south poles.  Shielded by crater rims and tall crater walls, the bottoms of those polar craters are cloaked in eternal darkness, and they are eternally cold.  Anything that happens to fall into one of those craters would freeze solid and could stay frozen for millions or even billions of years.

Back in the 1990’s, scientists began to suspect that those deep, dark craters around Mercury’s poles might be full of water (frozen water, obviously, but still… water).  And then in the 2010’s, NASA’s MESSENGER space probe took a closer look and confirmed it.  There is, in fact, water (in ice form) on Mercury.  Water on Mercury, of all places!

But I remind you again, the bottoms of Mercury’s polar craters are obscenely and stupidly cold.  Too cold for water to freeze the way it freezes on Earth.  On a molecular scale, the ice we find here on Earth has a neat and orderly crystalline structure.  Scientists call our Earthly kind of ice “ice Ih” or “hexagonal ice,” because the water molecules fit together in a hexagon pattern.  But the ice on Mercury is more likely to be what scientists call “amorphous ice.”

Amorphous ice is what happens when water freezes so fast that the water molecules don’t have time to arrange themselves in any sort of crystalline structure.  On a molecular scale, the water molecules are scattered haphazardly about.  No hexagons.  No patterns or shapes.  The ice is structurally shapeless—a.k.a., amorphous.  This doesn’t occur often here on Earth, except in certain astrophysics laboratories, but amorphous ice is extremely common out in space.

Comets and asteroids?  Whatever water they have is, partially or wholly, in the form of amorphous ice.  The surfaces of Europa, Ganymede, and the other icy moons of the outer Solar System?  They may be partially composed of amorphous ice.  And the ice inside those polar craters on Mercury (and similar polar craters on the Moon)?  You can bet on that being amorphous ice, too.

WANT TO LEARN MORE?

Water can freeze in so many different ways, with so many different crystalline and non-crystalline structures.  Here’s a brief video from Sci-Show about all the different kinds of ice scientists currently know about.

I also want to recommend this article from ZME Science, briefly summarizing the history of how water ended up on Mercury, how scientists on Earth first detected it, and how the MESSENGER mission later confirmed it.

Lastly, this is a far more technical source than the other two, but this paper on amorphous ice in the Solar System is the best source I could find stating, explicitly, that the ice on Mercury is probably amorphous ice. 

A to Z Challenge Theme Reveal

~ J.S. Pailly ~ 21 Comments

Hello, friends!

Do you have a favorite planet?  Each planet of the Solar System is beautiful in its own way, and weird in its own way, and dangerous in its own way.  It’s almost like each planet has its own distinct personality.  When you start learning about the planets, it’s hard to not pick a favorite.  My own favorite is Venus, but that’s not what I want to talk about today.  Today, I’m announcing my theme for this year’s A to Z Challenge, and that theme will be:

THE PLANET MERCURY

For those of you who don’t know, the A to Z Challenge is a month long blogging event.  Throughout the month of April, participants write twenty-six blog posts (starting with A, ending with Z) on a topic of their choice.  In previous years, I’ve used the A to Z Challenge as a platform to talk about scientific terminology, the search for alien life, and humanity’s future as a spacefaring species.  If you want to learn more about the A to Z Challenge, and if you’re interested in signing up yourself, please click here.

Now you may be wondering about the theme I picked this year.  Out of all space/science topics I could cover for an A to Z series, why the heck would I pick Mercury?  Mercury is not Mars, or Saturn, or Pluto.  Mercury is not a super exciting place.  There’s virtually no atmosphere.  There are absolutely no signs of life.  And if you’re thinking about future human habitats in space, Mercury may be the least appealing piece of real estate in the entire Solar System.

Observing Mercury with a telescope is inconvenient, due to Mercury’s proximity to the Sun.  Reaching Mercury with a spacecraft is also inconvenient, again due to the planet’s proximity to the Sun.  And what does all the inconvenience of observing Mercury or traveling to Mercury get you?  A grey rock.  There are a bunch of craters.  It gets really hot during the day, due (yet again) to the proximity of the Sun.  And there’s not a whole lot else worth saying about Mercury, right?

Wrong.  By the end of this year’s A to Z Challenge, I do not expect to change your mind about whatever your favorite planet happens to be.  My favorite planet will still be Venus.  But I do hope you’ll come to appreciate Mercury for what he truly is: a humble grey rock, with a few weird quirks, and a surprisingly big heart (by which I mean a surprisingly big planetary core–for such a small planet, Mercury has an enormous core!).

P.S.: I will be taking the rest of March off from regular blogging.  I’m still picking up the pieces after a recent family emergency, and I’ve decided that whatever free time I do have for blogging should go to preparing for this A to Z series.  So I’ll see you all on April 1st, when “A” will be for “amorphous ice.”