Geophysical and Planetary Delights
Scientists Exploring Planets
The American Geophysical Union began its fall meeting today in San Francisco and already there is some fascinating news coming out from the planetary science hive mind attendees. Of course I find it all interesting, but of particular interest today was a press conference (that I watched via the AGU press website) about a connection between solar wind disturbances and a “breathing” action — an expansion and contraction – of Earth’s upper atmosphere. One of the projects I’m working on right now is a series of video podcasts explaining how solar activity affects our atmosphere and magnetosphere, so this kind of information was right up our team’s alley!
There was also a rather startling result released by a group of scientists who maintain that a series of volcanic eruptions some 65 million years ago is what REALLY caused the death of the dinosaurs and not the impactor that carved out the Chicxulub meteor crater in Yucatan, Mexico. The team’s data show that the K-T extinction that we normally associate with the impact event actually coincided with the end of a major volcanism event in India. The volcanic outpouring spewed at least 30 times more sulfur dioxide, the suspected killing agent, than did the Chicxulub impact. In Mexico and Texas, melt rock spherules discovered in sediments well below the K-T boundary indicate that the Chicxulub impact predates the mass extinction by about 300,000 years, leaving no significant biotic effects.
This is all very fascinating, and I imagine that this result will spur some vehement discussions among the various proponents of different theories about the mass extinction of 65 MYA. However, I am a bit skeptical of the claim that an event that carved out a crater the size of the Chicxulub crater really didn’t have much effect on life. I think there’s still more work to be done to understand the entire sequence of events that led up to the ultimate demise of so many species around the time of the dinosaur die-off, and it will be interesting to see how it all works out.
Enceladus provides a tectonic feast for the eyes! Courtesy NASA and the Cassini Mission team.
Then there’s the ongoing excitement of Saturn exploration, in particular the Enceladus connection through Cassini. The closer the Cassini scientists look at Enceladus, the more they are convinced that this world is dynamic and active! In particular, the south pole surface changes over time scales that they can study with the spacecraft. That means it changes on the order of days or weeks!
Close-up observations show jets that spew water vapor and ice particles from beneath the surface — that’s what gives those “tiger stripes” that we see. The surface responds to pressure from below and you see giant cracks that have formed as the surface units shift.
What’s even more exciting is that along with the water vapor, scientists are seeing organic compounds and telltale signs of excess heat emerging from beneath the icy surface. There could be a liquid-water-rich zone beneath the ice where life could fluorish (if it exists).
Finally, among all the other press conferences was one given by the folks involved with the Mars Phoenix Lander that just went to sleep for good a few weeks ago. The data from this mission is far from being completely analyzed, but the team did point out that the arctic soil it studied is very cold and dry right now. However, long-term climate cycles could well make the planet moist enough to modify the soil’s chemistry. All this information is being folded into their models of the Mars long-term climatology and the action of water vapor as it moves from the atmosphere to the soil and back again.
The soil trench scooped up by the Mars Phoenix Lander. Courtesy NASA and the Mars Phoenix Lander team.
Peter Smith, the principal investigator for the Phoenix mission described what they found. “We have snowfall from the clouds and frost at the surface, with ice just a few inches below, and dry soil in between,” he said. “During a warmer climate several million years ago, the ice would have been deeper, but frost on the surface could have melted and wet the soil.”
Another one of the mission scientists, Ray Arvidson, commented further on the action of water on Martian soil. “The ice under the soil around Phoenix is not a sealed-off deposit left from some ancient ocean,” he said. “It is in equilibrium with the environment, and the environment changes with the obliquity cycles on scales from hundreds of thousands of years to a few million years. There have probably been dozens of times in the past 10 million years when thin films of water were active in the soil, and probably there will be dozens more times in the next 10 million years.”
The soil that Phoenix scooped up was cloddy (meaning that it clumped together). That clumpiness is one clue to the effects that water has on soil. The spacecraft did a microscopic study of the soil and found that it was made up of individual particles that are very likely windblown dust and sand. However, the clods of the soil hold together more cohesively than expected for unaltered dust and sand. Arvidson said, “It’s not strongly cemented. It would break up in your hand, but the cloddiness tells us that something is taking the windblown material and mildly cementing it.”
That cementing effect could result from water molecules adhering to the surfaces of soil particles. Or it could be from water mobilizing and redepositing salts that Phoenix identified in the soil, such as magnesium perchlorate and calcium carbonate. If you want to read more about this finding, zip on over to the Mars Phoenix mission site, where they have more details on the action of water and ice in the Martian soil.
I’ll be tuning in to AGU again tomorrow to hear the latest in geophysical and planetary science findings. You stay tuned, too!
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Thanks to Daniel Fischer, who writes the Cosmic Mirror pages, for alerting me to the online live press conferences. I’d gotten the notification about them, but in the excitement surrounding our recent power outages due to that nasty ice storm, I’d forgotten until he mentioned the conference to me in Twitter.
Re. the K/T event, presumably you’re writing about this:
http://www.agu.org/meetings/fm08/fm08-sessions/fm08_V22B.html
I guess, some volcanologists do no want to give up their dream of having solely killed off the mighty T-Rex! Theirs is a lost cause, imho.
Comment by changcho — December 16, 2008 #
Yes, that’s what I am referring to. It’s far more likely that the death of the dinosaurs and that huge mass extinction of 65 MYA was brought about by several factors, not the least of which was an impact event. The Deccan flows may well have precipitated climate changes that were instrumental in weakening some habitats and life forms; there could well have been other biological issues, too. I found the paper interesting, but not completely convincing as to its authors’ claim that it replaces the Chicxulub event as a main cause of the K/T extinction event.
The full story is yet to be told, AFAIAC.
Comment by ccp — December 16, 2008 #
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