Category Archives: Venus Express

'Casts, eclipses, transit of venus, venus, Venus Express

Things that Block Light

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Eclipses and Transits and More Eclipses, Oh My

A partial phase of the annular eclipse, shot through solar filter material using a Sony Cybershot. Copyright 2012 Carolyn Collins Petersen.

It’s been a banner couple of weeks for interesting celestial events. First, like many folks, I got to see the annular eclipse of the Sun on May 20th.  We went to southern Utah to get a clear view of the Moon slipping between Earth and the Sun and almost (but  not quite) blocking out all the sunlight. What we saw was a pretty amazing “ring” of light.  I took a few pictures, like the one here, but mostly I just sat and watched it.

We’ve chased a few eclipses now (we’re four for six), so instead of running around and trying to get the best pictures and video, we like to sit and watch. Oh, we did do some automated photography — just let the camera and timer do all the work.  But, mostly we watched. And were rewarded with a cool view that doesn’t come along very often.

In the national park where we viewed (Kolob Canyon, part of Zion National Park), we talked with various people who had driven over from California or Las Vegas or Colorado, and everyone seemed excited about the eclipse.  There were a few telescopes and cameras with solar filters set up, and a fair number of people using the pinhole projection method of viewing the eclipse. So, I was gratified to see that the campaign of “NEVER LOOK DIRECTLY AT THE SUN WITHOUT PROTECTION” was paying off.  It’s common sense, but still, in the heat of an eclipse sometimes even seasoned veterans forget the rule and take a peek, risking their eyesight forever.

The next big event is the Transit of Venus, which occurs June 5/6 (date depends on where you live), when Venus’s orbit will take it across the face of the Sun for several hours.  These don’t occur very often; they happen in pairs every hundred or so years, so the next one after this one will be in the year 2117.  If you’re inclined to take a look, the same rules apply: don’t look directly at the Sun, use proper filters (NOT SUNGLASSES), and enjoy!  There’s a ton of information out there about the transit, so if you want to know more about it, go here, or  here. I even talk about it in my monthly edition of “Our Night Sky” for Astrocast.TV, which you can watch below.

Finally, there’s a little bit of a lunar eclipse occurring tomorrow June 4th.  The best places for viewing this eclipse will be in and near the Pacific Ocean, according to the folks at eclipse.nasa.gov.  However, people in the Americas will see part of it, as will people in eastern Asia.  If you want to watch as part of the Moon slips through Earth’s shadow, get more information at the link above.

It’s kinda cool that three events that are the result of sunlight being blocked by celestial objects are occurring so close together. There’s nothing magical about it, but there is something fascinating to watch, so check out the transit and the eclipse (if they’re visible where you live).  Participate in observing!  That’s what astronomy’s all about!

 

 

planetary history, planetary climates, planetary science, planets, venus, Venus Express

Planetary Habitability

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What Does it Mean?

In my last blog entry, I talked about oceans on ancient Mars and the evidence for them that planetary scientists are finding in craters on the Red Planet. All the questions about water on Mars really point to a big question about habitability — that is, a world’s capability of sustaining life.  There’s a sort of rote list of things that planetary scientists recite when it comes to assessing what a world has to support living beings. It has to have water, warmth, and organic material (food, essentially) for the life to exist. Those things are important for habitability.  So, if Mars had water in the distant past, and if it had warmth (from volcanism or heating from its core or if it had an atmosphere that could trap heat), then two of the three conditions for life would have been met. Food — organic material — would be a simple chemical problem to solve. Here on Earth, food for life ranges from the stuff you and I eat every day to the needs of such one-celled beings as bacteria that munch on sulfur.  Obviously, early Mars didn’t have gourmet delights that we could eat, but it could well have had plenty of delicacies for one-celled organisms.  So, the planet could have been habitable.  If we decided to live there in the future, it could still be termed habitable, but only just barely and we’d have to bring along habitats to take advantage of the barely habitable landscape. But, it could be done. And, it likely will be done.

So, we know Earth is habitable (still). And, Mars was and could be. But, what about Venus?  You know, that beautifully bright starlike object that’s making a nightly curtain call in our western skies after sunset?  Yeah, that one.  It’s gorgeous to look at, but if you landed on Venus, you’d fry in an instant, if you weren’t crushed to death first by the hellishly heavy and hot atmosphere.  So, how could this volcanic, sulfurous world be habitable?  Clearly it isn’t right now, but it may have been in the past.

What early Venus could have looked like. Could it have had a water ocean? Or was it more likely a molten world with a wet atmosphere? What happened to it? Credit: J. Whatmore.

Scientists at the European Space Agency are operators for the Venus Express orbiter, which has sent back data suggesting very strongly that early Venus could have water — perhaps even an ocean of it — and may have begun its planetary life as a much more Earthlike world. The spacecraft measured the escape of molecules of hydrogen and oxygen from Venus out to space.  The rate of escape of hydrogen is roughly twice that of oxygen, and this indicates that water is the source of these escaping materials. There’s also a tracer element called deuterium that also tells scientists that water has been escaping the planet. Deuterium is a heavy form of hydrogen, and it would have more difficulty escaping the planet’s gravitational pull. The presence of large amounts of it in the upper atmosphere of Venus tells us that water has also escaped and left the deuterium behind.

It’s probably unlikely that Venus had Earthlike oceans as shown in the artist’s concept above.  If it did have standing water, those pools and/or small oceans could have been formed when comets slammed into the molten surface.  If that happened, and if conditions were right, Venus could have been habitable for a short time in its early history. If that’s true, then it begs the question of whether life could have arisen on the planet, only to be snuffed out by Venus’s subsequent changing climate.  It’s an interesting idea and one that needs to be explored more.

However, the more likely scenario is that the newborn Venus had no oceans, but sported a very wet atmosphere overlying the molten surface.  Over time, sunlight broke the water molecules into hydrogen and oxygen (a process known as “photodissociation”). The newly freed gases fled to space, leaving behind the deuterium. The escape process cooled things down enough, and the surface cooled.

There’s still a lot of “ifs” in these scenarios, but the evidence for water (past and present) is strong, based on the Venus Express data.  It’s a good hint that the Venus we see today — hot, arid, miserable, and volcanic — wasn’t always this way.  And, it adds more to our store of knowledge about just when a planet can be habitable in its history — provided the conditions are right.

Stay tuned!