What smacks into Ceres stays on Ceres, research suggests

What smacks into Ceres stays on Ceres, research suggests
Experiments using a high velocity cannon suggest that when asteroids hit targets that are icy or made of porous silicate materials, much of the impact material stays in the crater. The findings have implications for the surface composition of the dwarf planet Ceres. Credit: NASA Ames Research Center / Brown University

A new set of high-velocity impact experiments suggests that the dwarf planet Ceres may be something of a cosmic dartboard: Projectiles that slam into it tend to stick.

The experiments, performed using the Vertical Gun Range at NASA's Ames Research Center, suggest that when asteroids and other impactors hit Ceres, much of the impact material remains on the surface instead of bouncing off into space. The findings suggest the surface of Ceres could consist largely of a mish-mash of meteoritic material collected over billions of years of bombardment.

The research, by Terik Daly and Peter Schultz of Brown University, is published in Geophysical Research Letters .

Ceres is the largest object in the asteroid belt and the nearest dwarf planet to Earth. Until the recent arrival of the Dawn spacecraft, all that was known about Ceres came from . The observations showed Ceres to be mysteriously low in density, suggesting it is made either of very porous silicate material, or perhaps contains a large layer of water ice. Observations of its surface were remarkable as well—largely for being unremarkable.

"It's really bland in the telescopic observations," said Daly, a Ph.D. student at Brown and the study's lead author. "It's like someone took a single color of spray paint and sprayed the whole thing. When we think about what might have caused this homogeneous surface, our thoughts turn to impact processes."

And to understand impact processes, the researchers turned to NASA's Vertical Gun Range, a cannon with a 14-foot barrel that can launch projectiles at up to 16,000 miles per hour. For this work, Daly and Schultz wanted to simulate impacts into low-density surfaces that mimic the two broad possibilities for the composition of Ceres's surface: porous silicate or icy.

"The idea was to look at those two end-member cases, because we really don't know yet exactly what Ceres is like," Daly said.

For the porous silicate case, the researchers launched impactors into a powdered pumice. For the icy case, they used two targets: snow, and snow covered by a thin veneer of fluffy silicate material, simulating the possibility the Ceres's ice sits below a silicate layer. They then blasted these targets with pebble-sized bits of basalt and aluminum, simulating both stony and metallic meteorites.

The study showed that in all cases, large proportions of the impact material remained in and around the impact crater. This was especially true in the icy case, Daly said.

"We show that when you have a vertical impact into snow—an analog for the porous ice we think might be just beneath the surface of Ceres—you can have about 77 percent of the impactor's mass stay in or near the crater."

The results were a bit of a surprise, said Schultz, who has studied impact processes for many years as professor of earth, environmental, and planetary sciences at Brown.

"This is really contrary to previous estimates for small bodies," Schultz said. "The thought was that you'd eject more material that you'd collect, but we show you can really deliver a ton of material."

The impact speeds used in the experiments were similar to speeds thought to be common in asteroid belt collisions. The findings suggest that a majority of impacts on porous bodies like Ceres cause an accumulation of impact material on the surface.

"People have thought that perhaps if an impact was unusually slow, then you could deliver this much material," Schultz said. "But what we're saying is that for a typical, average-speed impact in the , you're delivering a ton of material."

Over billions of years of such impacts, Ceres may have accumulated quite a bit of non-native material, Daly and Schultz said, much of it mixing together to create the relatively nondesdescript surface seen from telescopes. The researchers are hopeful that as the Dawn spacecraft scans the surface at much higher resolution, it might be able to pick out individual patches of this delivered material. That would help confirm the relevance of these experiments to celestial bodies, the researchers say.

The results have implications for missions that aim to return asteroid samples to Earth. Unless the landing sites are carefully chosen, the researchers say, those missions could end up with samples that aren't representative of the object's original material. To get that, it might be necessary to find an area where there has been a relatively recent impact.

"You can't do this like the old claw crane from the arcade," Schultz said. "You can't just reach down and grab whatever's there. You may need to find a fresh where perhaps the native stuff has been churned up."


Explore further

Dawn glimpses Ceres' north pole

More information: Geophysical Research Letters, onlinelibrary.wiley.com/doi/10 … 015GL065601/abstract
Journal information: Geophysical Research Letters

Provided by Brown University
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Oct 14, 2015
suggest that when asteroids and other impactors hit Ceres, much of the impact material remains on the surface instead of bouncing off into space.


Yet more confirmation that my theory of water being more important than gravity for the formation of bodies is in fact leaning in the right direction.

It is true, if you think of these light bodies only in gravitational terms, you would think huge amounts of material should escape at high velocities, but when you consider both the cushioning behavior of water and the surface tension of any liquid water made by melt, you can see that material can be captured efficiently.

in fact, I think large amounts of water and water-ice is actually REQUIRED to efficiently grow low-mass bodies such as asteroids, comets, and dwarf planets.

When you think about a rocky/metallic target...a bullet bounces off that...

When you have a soft target (water) it is more likely to be "absorbed" by the material.

Oct 14, 2015
You see, the "softness" fo the ice allows a cushioning effect, slowing down the impactor more gradually than a rocky/metallic surface.

Then the crystal structure and the partial charge of the water-ice (as it refreezes) captures the dust and rocks...not the gravity itself...

This is how comets form, and this is how comets and asteroids efficiently deliver mass to infant planetesmals and dwarf planets without destroying them.

if you think it was efficient using stone or metal bullet (asteriod) should try modeling an even softer bullet (simulating a comet). Even more of it will be absorb and captured right near the impact crater.

I think what stopped Ceres from becoming a full planet is the gravity of Jupiter and Saturn.

However, this is a good thing for science, because it allows us to study a dwarf planet in a pristine environment (as opposed to an ice moon which is even more heavily influenced by gas giant gravity and such).

Oct 14, 2015
It is interesting that Pluto is much colder than Ceres, yet shows an atmosphere and so much geologic activity. Yes, it's a few times more massive, so I get that, but Ceres looks like a dead ball with some craters. Pluto looks like a sonar map of the floor of the Earth's oceans...like that deep, sub-surface mountain range east of the Antilles (forgive me, I don't know what it's called as I've never seen it labelled on a map).

Perhaps Pluto really does need to be upgraded to full planetary status again, or perhaps a new designation needs to be concocted for objects like Pluto since it fails to have "cleared it's own orbital environment" but otherwise shows characteristics of full blown planets.

Oct 14, 2015
When you have a soft target (Air) it is also more likely to absorb the kinetic energy and distribute it. Anything that distributes the energy transfer increases the amount of mass that is conserved. Look at Jupiter as a perfect example for a body that captures tons of material a day in the gravitationally thickened atmosphere. Water is nothing special, it just happens to be present in this case.

Oct 14, 2015
When you have a soft target (Air) it is also more likely to absorb the kinetic energy and distribute it. Anything that distributes the energy transfer increases the amount of mass that is conserved. Look at Jupiter as a perfect example for a body that captures tons of material a day in the gravitationally thickened atmosphere. Water is nothing special, it just happens to be present in this case.


To quote the android, David, "Big things have small beginnings." (queue eerie music).

The purpose of this experiment was to understand how small things in space get bigger...such as Ceres.

Oct 14, 2015
What I get from the article is that it might be a very good spot for mining materials if/when we finally get some sort of useful drive we can run around in local space with.

Oct 14, 2015
Pluto vs Ceres - Returners


Pluto - 15x Ceres

Charon - 2+x Ceres.

The colors of Pluto and Charon pictures are are fake. IF we saw them as they are, we'd see tinted gray orbs.

If you don't get this, ask yourself if you have ever looked at the night sky and viewed any of those rainbow colored space pics?

Also the NH and Dawn teams do things differently.

Pluto's team knows how to use "natural looking" colors and fun news to sell their mission.

The Ceres team are marketing dullards and don't enhance their photos at all.

Because the Dawn team doesn't highlight what it finds you miss all the fun stuff the Pluto team shares.

The differences you see are all related to how differently the two teams do their work more than anything else.

If the teams were switched, it'd be Ceres that impressed and Pluto would the gray boring one. LOL


Oct 14, 2015
@Returners tl;dr

Oct 15, 2015
Jonseer:

New Horizons has the ability to interpret color. They know Pluto has BLUE haze in it's atmosphere, and they know some of the ices and contaminants are pink/red, and some are not.

They have not explained how fresh mountain ranges form on a planet where the light (ficticious substance "energy") is so low compared to other planets.

I honestly expected Pluto to look like Ceres, because who would have expected something with so little light and mass to have active weather and Geology...and I don't think NASA expected to find that either....active glacial floes, mountains, you can see moraines and deltas for goodness sake..IT'S MORE ALIVE THAN MARS, and it was supposed to be a dead ball of ice.

I await the "Expert" explanation because they haven't given one yet.

Now I know, I nkow, water-ice and methane-ice can melt and vaporize at much lower temperature than rock, so maybe a tiny radioactive core can do all that...who knows...

Oct 15, 2015
We all understand surface softness. I know of no normal child who doesn't experiment with throwing or dropping stones into mud. But this article makes it sound like experiments conducted on Earth (Earth gravity) are being interpreted to indicate similar results at dwarf planet gravity. That sounds wrong. At dwarf planet gravity the softer surface material might be lost at a much higher rate, especially for impacts not arriving perpendicular to the surface. The projectile experiment conducted on earth I'll wager accelerates NONE of the surface material to escape velocity.
That being said, how else would planetary systems form if impacts never result in accumulation of material? I doubt any new knowledge has resulted from this research.....

Oct 15, 2015
The projectile experiment conducted on earth I'll wager accelerates NONE of the surface material to escape velocity.
Check this: "...you can have about 77 percent of the impactor's mass stay in or near the crater."
Apparently, they only focused on material that got stuck right upon impact and excluded the rest of the impactor's mass, whatever way gravity affected this last. So, you may consider it "Lost in Space" in regard to the experiments results.
I doubt any new knowledge has resulted from this research...
Well, it would be something really important to account for when they analyse Dawn's data, it's not?

Oct 16, 2015
Ceres is like a gigantic dust bunny. I bet those shiny parts are dimes and lost rings from keychains.

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