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Ceres organic matter.

New analysis reveals that Ceres’ spots harbor a lot of organic material

New research shows Ceres’ surface is dotted with organic matter — much more of it that we’ve previously realized. The findings raise questions regarding how this material came to be, and why it concentrates in patches.

Ceres organic matter.

Spots of organic material near Ernutet crater on the dwarf planet Ceres.
Credit: NASA / Hannah Kaplan.

There seems to be more to the organic material the Dawn craft discovered on Ceres last year than we initially thought. The patches of carbon-based compounds may contain a much higher abundance of organic matter than initial analysis revealed, according to a new analysis from Brown University.

Organic, free-range Ceres

“What this paper shows is that you can get really different results depending upon the type of organic material you use to compare with and interpret the Ceres data,” said Hannah Kaplan, lead researcher of the study. “That’s important not only for Ceres, but also for missions that will soon explore asteroids that may also contain organic material.”

The discovery of these organic patches on Ceres last year was made using the Visible and Infrared (VIR) Spectrometer on the Dawn spacecraft, which has been in orbit of the dwarf planet since 2015. The finding was met with enthusiasm at NASA and beyond: organic molecules are, after all, the building blocks of life. So, scientists are understandably keen on finding out how such matter is distributed on planets other than our own. The presence of these compounds on Ceres isn’t proof that there was once life on this bit of rock. However, it definitely increases the odds. Factor in that Ceres also boasts a sizeable stash of water ice, another fundamental requirement for life as we know it, and you get quite the exciting place.

The picture may get even better, however. Dawn’s VIR instrument analyzed the patches on Ceres’ surface using the way its surface interacts with incoming light. By looking at what wavelengths these patches reflected and absorbed, ground control could estimate their chemical makeup. In the region of Ernutet Crater (Ceres’ northern hemisphere), Dawn picked up signals consistent with organic molecules. Next, NASA needed to know just how much organic material they had found — so they compared the VIR data to similar readings performed on samples of organic material from Earth. Based on this comparison, they concluded that Ceres’ spots comprised roughly 10% organic matter.

Kaplan and her team, however, weren’t satisfied with the reference standard NASA used — so they re-did the comparison using a different one. Instead of using Earth-borne rocks, they used samples of carbonaceous chondrite meteorites. Previous analysis of such space rocks that fell to Earth revealed that they contained organic material that is slightly different from that native to our planet.

“What we find is that if we model the Ceres data using extraterrestrial organics, which may be a more appropriate analog than those found on Earth, then we need a lot more organic matter on Ceres to explain the strength of the spectral absorption that we see there,” Kaplan said.

“We estimate that as much as 40 to 50 percent of the spectral signal we see on Ceres is explained by organics. That’s a huge difference compared to the six to 10 percent previously reported based on terrestrial organic compounds.”

Unknown origin

The team proposes two possible explanations for how organic material popped up on Ceres in such high concentrations. They could either have been produced on Ceres itself and then blasted to the surface. Alternatively, they could have been delivered by impacts with organic-rich comets or asteroids.

In the case of delivery, comets are more likely culprits than asteroids — the former tend to have higher contents of organic material, around 40 to 50 percent, which would be consistent with Ceres’ patches. However, this explanation seems unlikely, the team notes. The violence and heat of these impacts would likely destroy a substantial amount of the original organic material, meaning we’d see much lower concentrations on the surface.

The other explanation, that of in-situ generation, is also problematic. Organic material has only been identified in small patches on Ceres’ northern hemisphere — and, if the team’s findings are correct, in high concentrations. It’s a lot of organic material spread over a very small area, and we have no idea how it could get like this.

“If the organics are made on Ceres, then you likely still need a mechanism to concentrate it in these specific locations or at least to preserve it in these spots,” said Ralph Milliken, a study co-author.

“It’s not clear what that mechanism might be. Ceres is clearly a fascinating object, and understanding the story and origin of organics in these spots and elsewhere on Ceres will likely require future missions that can analyze or return samples.”

It’s not all unanswered questions. The research will help improve our ability to analyze the chemical make-up of extraterrestrial bodies. The team hopes their findings will “provide a framework of how to better interpret data of asteroids and make links between spacecraft observations and samples in our meteorite collection.”

With NASA announcing that it discovered organic material on Mars just one week ago, it seems that the universe may be a much more organic place than we’d assumed.

The paper “New Constraints on the Abundance and Composition of Organic Matter on Ceres” has been published in the journal Geophysical Research Letters.

This perspective view of Marcia crater on the giant asteroid Vesta shows the most spectacularly preserved example of "pitted terrain," an unexpected discovery in data returned by NASA's Dawn mission. Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA/JHUAPL

Hints of water found on the giant space rock Vesta

Two studies conducted by scientists at NASA based on data gathered by the Dawn spacecraft, which orbited around the Vesta asteroid, showed that the giant space rock holds tantalizing signs of water on its surface – albeit in very small amounts, in the form of hydrated minerals.

This perspective view of Marcia crater on the giant asteroid Vesta shows the most spectacularly preserved example of "pitted terrain," an unexpected discovery in data returned by NASA's Dawn mission. Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA/JHUAPL

This perspective view of Marcia crater on the giant asteroid Vesta shows the most spectacularly preserved example of “pitted terrain,” an unexpected discovery in data returned by NASA’s Dawn mission. Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA/JHUAPL

These conclusions were drawn after scientists found that volatile, or easily evaporated materials, have colored Vesta’s surface in a broad swath around its equator. Again, concerning its geometry,  peculiar pothole-like features mark some of the asteroid’s surface where the volatiles, likely water, released from hydrated minerals boiled off and eroded the rock. These formations have been found to be extremely similar to those on Mars, however while the planet is known to have been abundant  in water at a time; these feature identified on Vesta, an asteroid, took scientists particularly by surprise.

Again, no actual water was found, but scientists explain that due to the high energy release during collisions with other space rocks, the hydrogen bound to the minerals was converted into water, which instantly evaporated and thus geologically shaped the asteroid. The holes that were left as the water escaped stretch as much as 0.6 miles (1 kilometer) across and go down as deep as 700 feet (200 meters).

“The source of the hydrogen within Vesta’s surface appears to be hydrated minerals delivered by carbon-rich space rocks that collided with Vesta at speeds slow enough to preserve their volatile content,” said Thomas Prettyman, the lead scientist for Dawn’s gamma ray and neutron detector (GRaND) at the Planetary Science Institute in Tucson, Ariz.

At first, the researchers hypothesized that it might be possible for ice water to survive on the surface of the asteroid, at its poles. However,  Vesta has no permanently shadowed polar regions where ice might survive, and is permanently exposed to sunlight in a cyclic fashion.

“These results provide evidence that not only were hydrated materials present, but they played an important role in shaping the asteroid’s geology and the surface we see today.”

The Dawn spacecraft left last month from Vesta’s orbit, which is the 2nd largest rock in the asteroid belt, and is currently heading for the dwarf planet of Ceres – the biggest rock in the asteroid belt.

The findings were described in two papers published in the journal Science.

source

NASA’s Dawn spaceship departs Vesta asteroid, heads for Ceres

It’s one asteroid down and one to go, for NASA’s Dawn spacecraft. After spending a year studying the Vesta asteroid and retrieving valuable information to Earth, Dawn is now ready to head for its next destination: Ceres.

A different world

Scientists expect Ceres to be very different from Vesta. Ceres is considered to be the largest asteroid in our solar system, accounting for about a third of all the mass in the asteroid belt; in fact, it is a dwarf planet (the only one in the inner system), discovered more than 200 years ago, in 1801 – however, it was thought to be a full sized planet at the moment.

Ceres highlights a rocky inner core, and an icy mantle, and many believe it might hold a liquid ocean beneath the icy surface. The 100 km mantle has more freshwater than the Earth, and while exobiologists haven’t speculated on this matter as much as with Europa, for example, there is a possibility of life existing in the liquid water – if there is such a thing on Ceres.

Leaving Vesta

Vesta is a large asteroid too, the second largest one in our solar system, after Ceres, of course, with a mean diameter of about 525 kilometers; among its notable features, there lies a mountain about three times taller than Mount Everest. After spending one year on Vesta, Dawn slowly powered up its ion thrusters, slowly spiraling away from it after it can finally break free from the gravitational field. However, since its antenna has been pointed away from Earth, researchers have to wait until Wednesday to know if everything went according to plan – pretty much like with the ‘seven minutes of terror‘, for Curiosity. Still, it’s not the same thing.

“It’s not a sudden event. There’s no whiplash-inducing maneuver. There’s no tension, no anxiety,” said chief engineer Marc Rayman of the NASA Jet Propulsion Laboratory, which manages the $466 million mission. “It’s all very gentle and very graceful.”

A new Dawn

The Dawn shuttle is about to reach a historical landmark, if it succeeds in its three year trip: it will become the first shuttle to ‘hook up’ with two different celestial bodies – in a bid to learn more about our solar system’s evolution, and the asteroids themselves.

During its one year stay at Vesta, Dawn was quite busy, using its cameras, infrared spectrometer, gamma ray and neutron detector to explore the asteroid from different altitudes, getting as close as 209 kilometers from its surface; and it wasn’t in vain: Dawn revealed quite a few surprises.

Scientists have long known Vesta is scarred at its southern pole, likely from an impact with a smaller asteroid, but a closer inspection revealed Vesta has another scar pretty close to the first one – evidence that it has been hit twice by asteroids in the last 2 billion years. The collision threw shrapnel like pieces of rock into outer space, some of them actually landing on Earth as meteorites.

Asteroids – friend and foe

Asteroids have been given a lot of attention lately – for varied reasons. There is of course the always present fear that some naughty asteroid might head for our planet and whack us to oblivion – though now NASA keeps track of virtually all near-Earth asteroids, and even with today’s technology, there are ways to deflect an asteroid.

President Barack Obama canceled a return to the moon in favor of landing astronauts on a yet-to-be-selected asteroid as a stepping stone to Mars, and perhaps even more interesting – a number of tech billionaires are planning to mine asteroids for rare metals (gold, platinum, iridium, etc).

Researchers expect a much changed story on Ceres. Unlike the rocky Vesta, the nearly spherical Ceres has a dusty surface with an icy interior.

“Almost everything we see at Ceres will be a surprise and totally different from Vesta,” Russell said.

Via NASA’s Jet Propulsion Laboratory