Tag: geology

Geologists, using computer models, have reconstructed the size and impact velocity of a giant asteroid that hit the Earth approximately 3.26 billion years ago.

11:51 am

Geologists, using computer models, have reconstructed the size and impact velocity of a giant asteroid that hit the Earth approximately 3.26 billion years ago.

This is a fascinating result, but it is very important to recognize its very large uncertainties. The article for example says almost nothing about how these conclusions were reached, except for this one paragraph:

Lowe, who discovered telltale rock formations in the Barberton greenstone a decade ago, thought their structure smacked of an asteroid impact. The new research models for the first time how big the asteroid was and the effect it had on the planet, including the possible initiation of a more modern plate tectonic system that is seen in the region, according to Lowe. [emphasis mine]

I have highlighted that one word because it reveals a great deal. What they did was to create a computer model of the data they had, which was merely very unusual geology spread over a certain region called the Barberton Greenstone Belt. Note also that this region is not where the impact occurred. “The study’s co-authors think the asteroid hit the Earth thousands of kilometers away from the Barberton Greenstone Belt, although they can’t pinpoint the exact location.”

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A new analysis of data from Messenger suggests that violent explosive volcanism occurred throughout much of Mercury’s history.

2:06 pm

A new analysis of data from Messenger suggests that violent explosive volcanism occurred throughout much of Mercury’s history.

What is interesting about this result is that previously it was believed that explosive volcanism didn’t happen at all on Mercury.

On Earth, volcanic explosions like the one that tore the lid off Mount St. Helens happen because our planet’s interior is rich in volatiles — water, carbon dioxide and other compounds with relatively low boiling points. As lava rises from the depths toward the surface, volatiles dissolved within it change phase from liquid to gas, expanding in the process. The pressure of that expansion can cause the crust above to burst like an overinflated balloon.

Mercury, however, was long thought to be bone dry when it comes to volatiles, and without volatiles there can’t be explosive volcanism. But that view started to change in 2008, after NASA’s MESSENGER spacecraft made its first flybys of Mercury. Those glimpses of the surface revealed deposits of pyroclastic ash — the telltale signs of volcanic explosions — peppering the planet’s surface. It was a clue that at some point in its history Mercury’s interior wasn’t as bereft of volatiles as had been assumed.

The new conclusions have not only found evidence of explosive volcanism, it found a wide range of ages for these deposits, indicating that the explosive volcanism took place across an extended period of time.

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New geological research suggests that the hydrogen levels that have detected on the moon — which are used to predict the presence of water — might be a false positive and not exist at the levels predicted.

11:17 am

The uncertainty of science: New geological research suggests that the hydrogen levels that have been detected on the moon — which are used to predict the presence of water — might be a false positive and not exist at the levels predicted.

Instead, what scientists thought was hydrogen in water molecules might be calcium as part of a mineral called apatite. If so, this would mean that the Moon has a lot less water than hoped. This data might also explain the lack of water seen in the Apollo samples as compared to what is suggested should be there from more recent orbital data. This also might explain the conflicting results from instruments on Lunar Reconnaissance Orbiter.

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Before and after images from Mars Reconnaissance Orbiter have discovered the formation of a new gully on Mars sometime between November 2010 and May 2013.

8:43 am

Before and after images from Mars Reconnaissance Orbiter have discovered the formation of a new gully on Mars sometime between November 2010 and May 2013.

The winding gully seems to have poured out from an existing ribbon channel in a crater in Mars’ Terra Sirenum region. The leading hypothesis on how the gully formed is that debris flowed downslope from an alcove and eroded a new channel. Though it looks water-carved, the gully is much more likely to have been formed when carbon dioxide frost accumulated on the slope and grew heavy enough to avalanche down and drag material down with it.

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Scientists think they have detected active volcanoes on Venus.

3:12 pm

Scientists think they have detected active volcanoes on Venus.

We should hear more about this story in the next couple of days, after the scientists give their presentation at a science conference today. Note too that this result would only confirm other data, such as the fluctuating levels of sulfur in Venus’s atmosphere, that have suggested active volcanoes hidden under that planet’s thick cloud cover.

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Orbital images from Mars Reconnaissance Orbiter have confirmed that the mysterious rock that appeared near Opportunity was not ejecta from a nearby meteorite impact.

2:29 pm

Orbital images from Mars Reconnaissance Orbiter have confirmed that the mysterious rock that appeared near Opportunity was not ejecta from a nearby meteorite impact.

The scientists theorized that there was a very remote chance that a nearby impact has thrown the rock into place, but the images show nothing nearby. Moreover, if there had been an impact we probably would have seen more rocks raining down all around. The images are further confirmation that the rock was kicked up by the rover itself as it rolled along.

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The geological history of Venus: What’s known, not known, and unknown.

11:48 am

The geological history of Venus: What’s known, not known, and unknown.

This is a very clearly written overview by James Head, one of the world’s preeminent planetary geologists, of what has been learned about the geology of Earth’s sister planet, the planet of a million volcanoes. Key quote:

Many features on Venus (folded mountain belts, rift zones, tesserae) were like Earth, but there were few signs of Earth-like plate tectonics, so that Venus seemed to have a single lithospheric plate that was losing heat conductively and advectively. But the cratering record presented a conundrum. First, the average age of the surface was <20% of the total age of the planet, and second, the average was not a combination of very old and very young surfaces, such as Earth’s continents and ocean basins. Third, the lack of variability in crater density, and of a spectrum of crater degradation, meant that all geological units might be about the same age. This implied that the observed surface of Venus must have been produced in the past hundreds of millions of years, possibly catastrophically, with very little volcanic or tectonic resurfacing since then! Suddenly, Venus was not like Earth, nor like the Moon, Mars, or Mercury.

Some scientists even believe that Venus was essentially resurfaced in a massive volcanic event about a half billion years ago. Others disagree. Meanwhile, the European probe Venus Express has gotten hints that volcanic activity is still going on.

As Head concludes, it has been 20 years since the last spacecraft arrived at Venus to do geological research. It is time to return.

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Photos taken 33 years ago by a photographer who died in the Mt. St. Helens eruption have been discovered and developed.

9:52 pm

Photos taken 33 years ago by a photographer who died in the Mt. St. Helens eruption have been discovered and developed.

Reid Blackburn took the photographs in April 1980 during a flight over the simmering volcano. When he got back to The Columbian studio, Blackburn set that roll of film aside. It was never developed. On May 18, 1980 — about five weeks later — Blackburn died in the volcanic blast that obliterated the mountain peak.

Those unprocessed black-and-white images spent the next three decades coiled inside that film canister. The Columbian’s photo assistant Linda Lutes recently discovered the roll in a studio storage box, and it was finally developed.

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Data from Messenger now shows that as Mercury cooled it shrunk far more than earlier data had indicated.

9:17 am

Data from Messenger now shows that as Mercury cooled it shrunk far more than earlier data had indicated.

A new census of these ridges, called lobate scarps, has found more of them, with steeper faces, than ever before. The discovery suggests that Mercury shrank by far more than the previous estimate of 2-3 kilometres, says Paul Byrne, a planetary scientist at the Carnegie Institution for Science in Washington DC. He presented the results today at a meeting of the American Geophysical Union in San Francisco, California.

The finding helps explain how Mercury’s huge metallic core cooled off over time. It may also finally reconcile theoretical scientists, who had predicted a lot of shrinkage, with observers who had not found evidence of that — until now. “We are resolving a four-decades-old conflict here,” Byrne told the meeting.

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Curiosity has succeeded in dating the age of one of its rock samples, the first time this has ever been done remotely on another planet.

12:33 pm

Curiosity has succeeded in dating the age of one of its rock samples, the first time this has ever been done remotely on another planet.

The second rock Curiosity drilled for a sample on Mars, which scientists nicknamed “Cumberland,” is the first ever to be dated from an analysis of its mineral ingredients while it sits on another planet. A report by Kenneth Farley of the California Institute of Technology in Pasadena, and co-authors, estimates the age of Cumberland at 3.86 billion to 4.56 billion years old. This is in the range of earlier estimates for rocks in Gale Crater, where Curiosity is working.

This is significant engineering and scientific news. In the past the only way to date the rocks on another world was to bring them back to Earth. This was how the moon’s geology was dated. On Mars, dating has only been done by crater counting, comparing those counts with those on the Moon, and then making a vague guess. To have the ability to date rocks remotely means that geologists can begin to sort out the timeline of Mars’s geology without having to bring back samples.

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New data suggesting the presence of granite on Mars also suggests that the planet is more geologically complex than previously believed.

9:17 am

The uncertainty of science: New data suggesting the presence of granite on Mars also suggests that the planet is more geologically complex than previously believed.

In my years of science writing, I can’t count the number of times I’ve written the phrase “more complex than previously believed.” For some reason, modern scientists seem to always assume that things will be simple, with one straight-forward answer. From gamma ray bursts to supernovae to planetary formation to whatever, the first example found and the first theory developed from that first example has repeatedly been expected to explain everything.

But that’s not how things work. Instead, the closer scientists have looked, the more complex and interesting things have always become. Many different things can cause gamma ray bursts. Supernovae come in many types. Solar systems don’t have to resemble ours. Everything is always more complex than you first believe.

Scientists would get things wrong less often if they simply kept this thought in mind, at all times.

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Geologists have determined that the magma reservoir under Yellowstone is much bigger than previously thought.

9:25 am

The uncertainty of science: Geologists have determined that the magma reservoir under Yellowstone is much bigger than previously thought.

Jamie Farrell, a postdoctoral researcher at the University of Utah, mapped the underlying magma reservoir by analysing data from more than 4,500 earthquakes. Seismic waves travel more slowly through molten rock than through solid rock, and seismometers can detect those changes.

The images show that the reservoir resembles a 4,000-cubic-kilometre underground sponge, with 6–8% of it filled with molten rock. It underlies most of the Yellowstone caldera and extends a little beyond it to the northeast.

The geologists also noted that the threat from a huge volcanic eruption is less of a concern than that of earthquakes.

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Asteroid 2012 DA14 might experience seismic activity when it zips pass the Earth tomorrow.

2:57 pm

Asteroid 2012 DA14 might experience seismic activity, an asteroid quake, when it zips pass the Earth tomorrow.

[MIT scientist Richard] Binzel imagines what an astronaut floating alongside such an asteroid might see: “The surface could slowly sway or rock by a few centimeters. Other things to look for would be puffs of asteroid-dust rising from the surface and gentle avalanches on the steepest slopes of craters.” In rare cases, “rubble pile” asteroids might break apart during the encounter and then re-form as Earth recedes into the distance.

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Want to learn something of the geology of the Grand Canyon?

2:10 pm

Want to learn something of the geology of the Grand Canyon? The Geological Society of America has just published a special volume of papers, with the introductory and afterword [pdf] chapters available online.

Those two chapters provide a very good layman’s summary of the geological state-of-the-art of the Grand Canyon. Very worthwhile reading if you plan to hike down in the near future.

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