Monthly Archives: April 2009

Mars

Visiting Mars

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Closeup on the Red Planet

I’m working on a new program about Mars and the latest discoveries the various spacecraft missions have been delivering up for planetary scientists. No matter how you look at it, Mars is fascinating. The more we look, the more we find. And the more we find, the more questions we have about this desert world.  I’ve been looking at Mars rover images and also at some of the stunning scenes available from the HiRise Camera on the Mars Reconnaissance Orbiter spacecraft. This mission is cranking out images every day, giving us a close to “real time” view of the planet.

The main thing that I think every time I see Mars images is just how ancient the place seems. The volcanoes are dead (or at least very quiescent), the landscapes are covered in layers of windblown dust, and stunningly shaped dunes sprawl across various places. In some places, everything seems to be eroding away (if slowly).  This is the face of change on Mars — spurred by seasonal weather variation, windblown erosion, and the occasional cratering event. As the seasons progress, ice melts, carbon dioxide outgasses, and water ice melts and sublimates. All these events alter the surface in different ways.

Ganges Chasma as seen by the HiRise camera on the Mars Reconnaissance Orbiter. (Click to embiggen.)
Ganges Chasma as seen by the HiRise camera on the Mars Reconnaissance Orbiter. (Click to embiggen.)

One of the most dramatic places on the planet is Valles Marineris, that long sunken trough and canyon network that hacks across a third of Mars’s surface. HiRise looked at a small section of Ganges Chasma, which is a trough that makes up part  of Valles Marineris.  The image is just stunning.

Long ago, the surface of Mars in this region was flooded by lava flows. After that, time and wind began changing the surface. Windblown dust and sand covered up everything. If you click on the image and examine the larger version more closely, particularly the region near the edge of this chasm, it looks brighter and smoother than the lava flows underneath.  Could this be sediments put in place by flowing water?  Or did an explosive v0lcanic event layer the region with fine dust?  Or, was it the work of the incessantly blowing Martian winds depositing layer upon layer of fine dust? A combination of all these factors?

Then, of course, you should explore the inner walls of this chasm. They look familiar, especially if you’ve ever been to areas on Earth where water has carved through canyon walls to reveal layers of rock.  Valles Marineris itself is a huge crack in the surface that formed a long time ago and affected by volcanic stress at one end and erosion along its entire length. There’s also some possibility that parts of Valles Marineris could have been carved out by the action of water or carbon dioxide.

It’s tough to tell the whole story of Mars in a short program, but if I had to summarize Mars and its surface history in a few words, it would be dry, dusty, cold, ancient, changing slowly by degrees.  It’s far from a dead world — just a very quiet and slowly changing one.

As I was writing this entry, I happened to hop over to Bad Astronomy. Phil Plait has also been touched by Mars today — go see what’s got him going!

International Dark-Sky Association, light pollution

Heads Up, Lights Out

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International Dark-sky Week

Do you have a lot of outdoor lights? What does your electric bill look like every month?  High?  Low?  Where do you live? The city? Not the city?  What do your night skies look like?  Barely see a few stars? More than a few? A whole starry night?

The answers to all those questions are related to at least one thing: excessive use of light.  Humans put out an incredible amount of light pollution, as if we want to advertise to the universe that we are so wealthy we can afford to light up the night. Of course this isn’t true.  We just like to light up the night, for reasons that have less to do with wealth and more to do with some perceived fear that if we don’t, bad things will happen. Or we won’t sell as many cars, or attract people to our strip malls, or people won’t be able to see how great our leaders are because their monuments won’t be lit up, or whatever it is people need to illuminate. It’s not that these uses of light should be stopped — but they should be done more efficiently, with an eye toward saving money, resources, and the night sky.

The International Dark-sky Association is encouraging people to celebrate better lighting at night by turning off the lights (or at least using them more sensibly) during Dark-sky Week, April 20-26.  The idea is for us all to figure out ways to use our lighting better in the long run — not just to eliminate light pollution, but to make positive contributions to our environment and our own health.  There are a number of studies, which IDA has references to on their extremely useful website, that point out how to better light our properties (with downward facing lights so that light isn’t scattered to the sky), how darkness is important for all forms of life, and how eliminating unnecessary lighting can help us use less energy and reduce pollution. It’s a win-win for everybody, even the folks who feel the need to have security lights (which can be made to work more efficiently and focus exactly where needed, rather than splashily illuminating areas without regard to sensible use).  If you light properly, your electric bills will go down, your community will benefit, and so will you.

So, think about celebrating Dark-sky Week along with millions of people around the world. It’s a great time to assess how you can save money by using good lighting practices, and — as an added bonus — it’s a chance to skygaze at night after you’ve turned off the lights you don’t need. (Obviously, some safety lighting is necessary — make sure that it’s aimed properly and used well.)