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planetary_exploration (3)

Asteroid Stuff...

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An artist's depiction of an asteroid collision in outer space.(Image: © Don Davis, Southwest Research Institute)

 

Topics: Asteroids, Astrobiology, Planetary Exploration, Planetary Science


"We are made of star stuff." Carl Sagan

Consider the possibility that an asteroid may have transformed the picture of life on Earth — but forget the dinosaurs and the massive crater, and rewind an extra 400 million years from that dramatic moment.

Back then, life was primarily an oceanic affair and backbones were the latest in arrival on the anatomy scene. But unlike the asteroid that killed the dinosaurs 66 million years ago, this earlier space rock never made it to Earth. Instead, a collision in the asteroid belt flooded the solar system with so much dust that, given some other changes at the time, allowed life on Earth to flourish, new research suggests.

"Most important events in the history of life are like that," said Rebecca Freeman, a paleontologist at the University of Kentucky who specializes in this period but wasn't involved in the new research. "You get a really unique set of circumstances that all come together, and you get a really dramatic event that maybe seems like it should be due to one particular dramatic thing. But in reality, it's a more complicated system at play," she told Space.com.

The dramatic event scientists want to explain is a spree of new species. That outburst of life, which paleontologists call the Great Ordovician Biodiversification Event, took place in the oceans, which were inhabited mostly by spineless creatures. "This is really a world that is dominated by invertebrate marine organisms," Freeman said. "Probably the top predator would have been a cephalopod," likely an ancestral relative of today's chambered nautilus, with its intricate spiral shell.

But when Birger Schmitz, a geologist at Lund University in Sweden, went hunting for rock dating back 466 million years, he wasn't hoping to find fossilized nautiluses; he was looking for fossilized meteorites. And over the past couple of decades, he and his colleagues have found dozens of these fossilized meteorites in a Swedish limestone quarry. Each carries a chemical time stamp indicating that it was heated about 470 million years ago, and scientists have thought for a while that there might have been a massive asteroid collision around that time.

 

Asteroid Dust Triggered an Explosion of Life on Earth 466 Million Years Ago
Meghan Bartels, Space.com

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Brine Europa...

Salt-laden water welling up from below gives Europa’s fissures and cracks their distinctive color.
Credit: NASA, JPL-Caltech and SETI Institute

 

Topics: Astrobiology, Exoplanets, Planetary Exploration, SETI


The sea sloshing beneath the icy surface of Jupiter’s moon Europa just might be the best incubator for extraterrestrial life in our solar system. And yet it is concealed by the moon’s frozen outer shell—presenting a challenge for astrobiologists who would love nothing more than to peer inside. Luckily they can catch a partial glimpse by analyzing the flavor of the surface. And the results are salty.

A new study published this week in Science Advances suggests that sodium chloride—the stuff of table salt—exists on Europa’s surface. Because the exterior is essentially formed from frozen seawater, the finding suggests that Europa’s hidden sea is drenched in table salt—a crucial fact for constraining the possibilities for life on the alien world.

Not that scientists have tasted a slice of the distant moon. To analyze Europa’s composition, astronomers study the light emanating from its surface, splitting it into a rainbow-like spectrum to search for any telltale absorption or emission lines that reveal the world’s chemistry. There is just one problem: Ordinary table salt is white and thus gives off a featureless spectrum. But harsh radiation—which exists at Europa’s surface in abundance—just might add a dash of color. That much was realized in 2015 when two NASA planetary scientists Kevin Hand and Robert Carlson published a study suggesting the yellowish-brown gunk on Europa might be table salt baked by radiation. To reach that conclusion, Hand and Carlson re-created the conditions on Europa within vacuum chambers—or as Hand calls them, “stainless steel shiny objects that are humming and whizzing.” Next, they placed table salt into those chambers, lowered the pressures and temperatures to simulate Europa’s surface, and blasted the samples with an electron gun to simulate the intense radiation.

 

Water on Europa—with a Pinch of Salt, Shannon Hall, Scientific American

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Mars Quake...

Model of the spaceship Insight, NASA's first robotic lander, dedicated to study the deep interior of Mars. REUTERS/Mike Blake/File Photo

 

Topics: Geophysics, Mars, NASA, Planetary Exploration


Finals are over. I'll be with our new granddaughter and her parents next week, along with working on my thesis, following up on my PhD application and changing diapers. My posts will be sporadic since I'll be on the road. I'll catch up.

The breakthrough came nearly five months after InSight, the first spacecraft designed specifically to study the deep interior of a distant world, touched down on the surface of Mars to begin its two-year seismological mission on the red planet.

The faint rumble characterized by JPL scientists as a likely marsquake, roughly equal to a 2.5 magnitude earthquake, was recorded on April 6 - the lander’s 128th Martian day, or sol.

It was detected by InSight’s French-built seismometer, an instrument sensitive enough to measure a seismic wave just one-half the radius of a hydrogen atom.

The lunar and Martian surfaces are extremely quiet compared with Earth, which experiences constant low-level seismic noise from oceans and weather as well as quakes that occur along subterranean fault lines created by shifting tectonic plates in the planet’s crust.

Mars and the moon lack tectonic plates. Their seismic activity is instead driven by a cooling and contracting process that causes stress to build up and become strong enough to rupture the crust.

Three other apparent seismic signals were picked up by InSight on March 14, April 10 and April 11 but were even smaller and more ambiguous in origin, leaving scientists less certain they were actual marsquakes.

 

NASA probe detects likely 'marsquake' - an interplanetary first
Joey Roulette, Reuters Science

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