Dwarf planet Ceres: 'A game changer in the solar system'

Dwarf planet Ceres: 'A game changer in the solar system'
Light reflecting from Ceres provides insight into its surface features. The section of spectrum between 2.7 and 3.3 resembles (though is not exactly like) pure water, while the dip at 3.3 revealed the presence of carbonates on the dwarf planet's surface. Credit: Hiroi, T. and M. E Zolensky, C. M. Pieters, M. E. Lipschutz, (1996)

In March of 2015, NASA's Dawn mission will arrive at the dwarf planet Ceres, the first of the smaller class of planets to be discovered and the closest to Earth. Ceres, which orbits the Sun in the asteroid belt between Mars and Jupiter, is a unique body in the Solar System, bearing many similarities to Jupiter's moon Europa and Saturn's moon Enceladus, both considered to be potential sources for harboring life.

On Thursday, August 15, Britney Schmidt, science team liaison for the Dawn Mission, and Julie Castillo-Rogez, from JPL, spoke in an Google Plus Hangout titled 'Ceres: Icy World Revealed?' about the growing excitement related to the innermost icy body.

"I think of Ceres actually as a game changer in the Solar System," Schmidt said. "Ceres is arguably the only one of its kind."

The innermost icy body

When Ceres was discovered in 1801, astronomers first classified it as a planet. The massive body traveled between Mars and Jupiter, where scientists had mathematically predicted a planet should lie. Further observations revealed that a number of small bodies littered the region, and Ceres was downgraded to just another asteroid within the asteroid belt. It wasn't until Pluto was classified as a dwarf planet in 2006 that Ceres was upgraded to the same level.

Ceres is the most massive body in the , and larger than some of the icy moons scientists consider ideal for hosting life. It is twice the size of Enceladus, Saturn's geyser-spouting moon that may hide liquid water beneath its surface.

Unlike other asteroids, the Texas-sized Ceres has a perfectly rounded shape that hints toward its origins.

"The fact that Ceres is so round tells us that it almost certainly had to form in the early solar system," Schmidt said. She explained that a later formation would have created a less rounded shape.

The shape of the dwarf planet, combined with its size and total mass, reveal a body of incredibly low density.

"Underneath this dusty, dirty, clay-type surface, we think that Ceres might be icy," Schmidt said. "It could potentially have had an ocean at one point in its history."

"The difference between Ceres and other icy bodies [in the Solar System] is that it's the closest to the Sun," Castillo-Rogez said.

Less than three times as far as Earth from the Sun, Ceres is close enough to feel the warmth of the star, allowing ice to melt and reform.

Investigating the interior of the dwarf planet could provide insight into the early solar system, especially locations where water and other volatiles might have existed.

"Ceres is like the gatekeeper to the history of water in the middle solar system," Schmidt said.

Studying the surface

As large as Ceres is, its distance has made it a challenge to study from Earth. Images taken by the space-based Hubble Space Telescope provided some insight to its surface, but to be sighted, features could be no larger than 25 kilometers in diameter. Several round circular spots mar the terrain, features which Schmidt said could be any one of a number of geologic terrains, including potentially impact basins or chaos terrains similar to those found on Europa. The largest of these, named Piazzi in honor of the dwarf planet's discoverer, has a diameter of about 250 kilometers. If this feature is an impact basin, it would have been formed by an object approximately 25 km in size.

But for Schmidt, this is another possible indication about the dwarf planet's surface.

Dwarf planet Ceres: 'A game changer in the solar system'
Ceres' round shape indicates that it formed early in the life of the solar system. Ceres lies in the center. Clockwise from the lower left: 2 Pallas, 4 Vesta, 243 Ida, 433 Eros, 25143 Itokawa, 951 Gaspra, 5535 Annefrank. Credit: Composite image of NASA mission and HST images: Schmidt, Britney Elyce, Characterizing the protoplanets : observations and geophysics of Pallas, Vesta and Ceres, PhD Dissertation, University of California at Los Angeles, June 2010

"It doesn't mean that Ceres hasn't been hit by something bigger than 25 kilometers," she said."It just means that whatever is going on on Ceres has totally erased [the topographic signature of that event]."

Ceres may have suffered major impacts, especially during periods of heavy bombardment early in the Solar System's history. If the surface contained ice, however, those features may have been erased.

Telescopes on Earth have also been able to study the light reflecting from the planet and read its spectra.

"The spectrum is telling you that water has been involved in the creation of materials on the surface," Schmidt said.

The spectrum indicates that water is bound up in the material on the surface of Ceres, forming a clay. Schmidt compared it to the recent talk of minerals found by NASA's Curiosity on the surface of Mars.

"[Water is] literally bathing the surface of Ceres," she said.

In addition, astronomers have found evidence of carbonates, minerals that form in a process involving water and heat. Carbonates are often produced by living processes.

The original material formed with Ceres has mixed with impacting material over the last 4.5 billion years, creating what Schmidt calls "this mixture of water-rich materials that we find on habitable like the Earth and potentially habitable planets like Mars."

Dwarf planet Ceres: 'A game changer in the solar system'
Comparing the habitability of Earth to Jupiter's icy moon Europa and the dwarf planet Ceres. Credit: Dawn EPO CosmoQuest

A prime site for life?

Water is considered a necessary ingredient for the evolution of life as we know it. Planets that may have once contained water, such as Mars, as well as moons that could contain it today, like Enceladus and Europa, are all thought to be ideal for hosting or having once hosted life.

Because of its size and closeness, Schmidt calls Ceres "arguably more interesting than some of these icy satellites."

"If it's icy, it had to have an ocean at some point in time," she said.

Castillo-Rogez compared Earth, Europa, and Ceres, and found that the dwarf planet bore many similarities to Earth, perhaps more than Jupiter's icy moon. Both Earth and Ceres use the Sun as a key heat source, while Europa takes its heat from its tidal interaction with Jupiter. In addition, the surface temperature of the dwarf planet averages 130 to 200 degrees Kelvin, compared to Earth's 300 K, while Europa is a frosty 50 to 110 K.

"At least at the equator where the surface is warmer, Ceres could have preserved a liquid of sorts," Castillo-Rogez said.

Liquid water could exist at other points on the dwarf planet known as cold traps, shadowed areas where frozen water could remain on the surface. Such icy puddles have been found on Earth's moon.

"The chemistry, thermal activity, the heat source, and the prospect for convection within the ice shell are the key ones that make us think that Ceres could have been habitable at least at some point in its history," Castillo-Rogez said.

Dwarf planet Ceres: 'A game changer in the solar system'
The dwarf planet Ceres as seen by the Hubble Space Telescope. Credit: NASA, ESA, J. Parker (Southwest Research Institute), P. Thomas (Cornell University), L. McFadden (University of Maryland, College Park), and M. Mutchler and Z. Levay (STScI)

The future of Ceres

As scientists develop more information about Europa and Enceladus, there has been a greater call to investigate the two prime sites for life. But Schmidt and Castillo-Rogez think that Ceres could also be a great boon for astrobiology and space exploration.

"It's not a difficult environment to investigate," she said."As we think about the future of landed missions for people and rovers, why not go to Ceres?"

Though it would be more challenging to drill into than Europa, which boasts an icy surface layer, the dwarf planet would make a great site to rove around on. Schmidt also noted that it could make a great launching point when it comes to reaching the outer . Its smaller mass would make it easier to land on—and leave—than Mars, which could make it a good site for manned missions.

"We have such a big planet bias, we have such a bias for things that look exactly like us," Schmidt said.

"In this kind of special place in the Solar System, we have a very unique object that might be telling us a lot about what we don't know about building a habitable planet."

Dwarf planet Ceres: 'A game changer in the solar system'
Ceres is thought to contain a thin outer layer of dust and rock over an icy layer. Credit: NASA/ESA/STScI

NASA's Dawn mission launched September 27, 2007. It traveled to the asteroid Vesta, where it remained in from July 2011 to July 2012 before heading to Ceres. It is slated to spend five months studying the , though Schmidt expressed hope that the craft would continue working beyond the nominal mission, allowing the team to study the icy body even longer.

Castillo-Rogez pointed out that not only will Dawn reach Ceres in 2015, the European Space Agency's Rosetta spacecraft will be escorting the comet Churyumov-Gerasimenko around the Sun that year, while NASA's New Horizons mission will be reaching Pluto and its moon Charon.

"'15 is going to be a great year for icy bodies," Castillo-Rogez said.

"I think when we get to Ceres, it's just going to be an absolute game changer, a new window into the Solar System that we wouldn't have without going there," Schmidt said.

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Aug 29, 2013
Ideal material for the construction of colonies at the laGrange points.
First in, best dressed.

Aug 29, 2013
Soon we will see the Shattered Sea!

Aug 29, 2013
There could be chemical weathering of space rocks on the surface of that world. Where else would all the clay come from? Almost all the minerals that were present on Ceres before the ice formed would now be beneath the water layer. Perhaps the combination of various sorts of radiation and some amount of water vapor could have hydrated the mafic minerals in the the meteorites - or perhaps some kind of biology is at work.

Aug 29, 2013
Soon we will see the Shattered Sea!

I was rather hoping for the Heechee.

Aug 29, 2013
"Here's Ceres!"

Ceres as waystation or extended research: There is no "cold fusion energy source". But solar panels would work well (works out to Jupiter now, at the very least).

Aug 30, 2013
Schmidt also noted that it could make a great launching point when it comes to reaching the outer solar system. Its smaller mass would make it easier to land on—and leave—than Mars, which could make it a good site for manned missions.

Certainly it's easier to take off of than Mars, but is it really the case that landing is easier?

Technologically, probably. But it seems like when dealing with probes - landers in particular - "difficulty" = weight, and that's pretty much the final word. On Mars, we have some atmosphere that we can use for aerobraking and to bleed off speed during descent. On Ceres, you have to carry enough fuel AND a rocket engine large enough to do a pretty major burn to bleed off every drop of the differential speed of the craft and Ceres upon arrival. Is all of that lighter than a heat shield and inflatable air bags?


Aug 30, 2013
Ceres is also farther away than Mars, so presumably the ideal transit speed for the craft would be higher, meaning more speed to bleed off. In addition to no atmosphere for aerobraking, Ceres also has much less gravity to assist during an orbit insertion maneuver, if the mission called for assuming orbit before performing descent.

You could also take an annoyingly long route that has the craft catching up to Ceres following it around the Sun, probably after at least 1 Earth assist - using an ion thruster to slow down for perhaps years before a matched-speed rendezvous. 3-5 year voyage.

Easier? Maybe. Better? I'm not convinced.

Aug 30, 2013
There is no "cold fusion energy source"
So do you think, that for example http://www.youtub...mOQXBS68 are describing BS and their authors are complete imbeciles?

BTW The fact some people like you are denying something means nothing. In the USA 60%+ Americans deny evolution. With compare to it the cold fusion is still supported wildly...;-) We should simply face the fact, that some people will always deny the reality despite of all evidence, if it will contradict their religion and/or state of mind.

Man, this is an article about an asteroid. Seriously?

Aug 30, 2013
This comment has been removed by a moderator.

Sep 02, 2013
"difficulty" = weight, and that's pretty much the final word.

I think it's a bit more complicated. Mass is a factor, but also whether there is an atmosphere or not or whether the gravity is strong or not.

With weak gravity you can use much weaker (smaller) engines. Also stuff like airbags become an option.

On Mars, we have some atmosphere that we can use for aerobraking and to bleed off speed during descent.

Very little. Mars atmosphere is only 1% as dense as that on Earth. (Actually it's favorable that Ceres has even less atmosphere since you don't need to worry about adding ablative shielding)

Ceres is also farther away than Mars, so presumably the ideal transit speed for the craft would be higher, meaning more speed to bleed off.

Ceres is in the asteroid belt which should mean plenty of other bodies nearby which you can use as swing-by partners to shed speed. In any case it'll probably be an ion thruster probe. So plenty of time to gain/shed speed.

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