It’s Windy on Mars!

Dust Devils Just Keep on Dancing Across Mars

Okay, a few weeks ago we had a week’s worth of high winds where I live, typical for Colorado in the late winter.  We call ’em Chinook winds, and they tend to dry things out as they blow at speeds upwards of 70 to 90 mph (112-144 km/hour) and gusts up above 100 (160 km/hr).  That’s all part of a weather pattern that occurs here, and in other parts of the world as the seasons change.  Right now, as we saw in Texas a few days ago, the winds and the associated weather patterns whip up twisters, tornadoes, dust devils.

The winds blow on Mars, too, and the Mars Reconnaissance Orbiter’s High Resolution Imaging Science Experiment (HiRISE) camera has been very good at spying out Martian dust devils.  Unlike a tornado which we see here on Earth, a dust devil typically forms on a clear day when the ground gets heated by the Sun. That warms the air just above the ground, and that air rises quickly through a small pocket of cooler air above it. If the conditions are just right, the air can start to rotate, and as it does, it picks up dust.  This is a  frequent occurrence on Mars.

HiRise view of a dust devil on Mars, taken March 14, 2012. Courtesy NASA/HiRise Team.

On March 14th, HiRISE caught sight of a Martian dust devil roughly 12 miles high (20 kilometers) whirling through a region called Amazonis Planitia.   The dust devil about (70 yards, or just about 70 meters across). The image was taken during late northern spring, two weeks short of the northern summer solstice, a time when the ground in the northern mid-latitudes heats up in the sunlight.

One of the cool things about these dust devils is that they scour the ground of dust, leaving behind a thin, sinuous little path. When those little paths were discovered, their appearance and cause was unknown. It didn’t take long for scientists to connect them with the appearances of dust devils. It appears that these dust devils are one mechanism by which dust gets redistributed around the Martian surface.

Check out the full story and a very cool animation showing what the dust devil might look like from the side at the NASA Mars Reconnaissance Orbiter page. It’s full of wooty Mars goodness!  And, if you experience winds and dust devils where YOU live on Earth, then you have a good idea of what it’s like on Mars when one goes twisting by!

 

 

Stars at Sea

Speaking of Astronomy…

When I’m not writing books or blog entries or writing scripts for documentaries about astronomy, I spend some time at sea each year as an enrichment speaker on cruise ships.  I began doing these in 2001, and over the years have spoken to thousands of people aboard various sizes of cruise ships about astronomy and space science. Lately I’ve been doing them on behalf of the Smithsonian Institution and their travel department, a relationship that I’m very pleased to maintain.

You’d think that cruising would be a great time to spend under the stars — and oftentimes, it is.  There you are, out in the middle of the ocean, nothing but you, the stars, the ship, and a crowd of people onboard.  What’s not to like?

Sometimes however, as happens on land, clouds encroach, there’s light pollution obscuring the view, and as in “real life” (instead of “vacation life”), other activities impinge on the time for stargazing. Cruise ship activity directors are employed to make sure that you have something to do (if you want to), whether it’s talks from people like me (and the other speakers), dancing, eating, learning a craft, taking in a show, and many other activities.

Still, when the conditions are right, the skies are clear and the lights are low, there’s nothing like standing up on the top deck, out in the middle of the ocean, and admiring the view.  I remember one of my early cruises, the captain would turn off all the lights up there and we’d bask in the starry skies. On the flip side, I was once on a ship that had a huge “jumbo-tron” movie screen on the top deck and the light pollution was enough to drown out all but the brightest stars and planets. So, the romance of the stars at sea has various realities, not all of them good ones.

One of the things I enjoy most is talking one-on-one with my fellow passengers. I encourage folks to ask any questions they want about astronomy, and the results are always amusing and enlightening. One time, I had just finished a presentation about some of the major discoveries made by the Hubble Space Telescope, and in the Q&A a person asked me about the nature of time and space.  Another time on a cruise around South America, I had a wonderful conversation up top with a rabbi about the nature of the stars.  After another I gave talk about the Moon, a fellow got up and asked me if I knew how the Apollo missions’ orbits were plotted. Turned out he was a retired JPL employee and had spent part of his career working on just that very problem.

And, the questions don’t just come from the passengers. One memorable night off the coast of Chile, we were standing out on the back deck and our table steward approached me with a question about astronomy. Mark and I ended up giving him a little private star party, and he shared with us some of the star legends of his society.  You can’t beat astronomy for bringing people together!

One of the most frequently asked questions I get is “how can we tell cosmic distances?”  People also ask me about things they’ve read in the media — such as the latest exoplanet discovery — and it gives me a lot of insight into how the media is handling such science topics.

What I like is that people are so darned interested in the stars. I often hear from someone that they used to have a telescope when they were a kid, or that they always loved going to the planetarium when they were in school.  So, it seems that astronomy is a universal topic we can all relate to. The truth is, no matter where I go in the world, people do have an interest in the skies.  We all share the skies, and grow up under the same sky — no matter where we call home. That’s a very valuable lesson to learn, no matter where you cruise in your life.

Speaking of stargazing, check out this month’s edition of “Our Night Sky”, the video stargazing tour I do each  month for Astrocast.TV.  It hits some of the high points of April’ s night skies — just enough to give you a taste of what’s up.  Use it as a springboard for your own stargazing adventures!