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#51 2007-09-12 05:42:19

cIclops
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Registered: 2005-06-16
Posts: 3,230

Re: Dawn - Vesta & Ceres orbiter

07pd2445-m.jpg
Back inside the mobile service tower on Launch Pad 17-B at Cape Canaveral
Air Force Station, the Dawn spacecraft waits for mating with the Delta II
- imaged 11 Sep 2007


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#52 2007-09-18 08:55:20

cIclops
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Re: Dawn - Vesta & Ceres orbiter

Dawn Journal 14 Sep 2007 - Marc Rayman, Project Engineer

As with most missions, the Dawn team finished designing the launch trajectory before the spacecraft was fully assembled. To ensure that the parameters loaded into the rocket's guidance computer would be correct, engineers planned for the maximum possible spacecraft mass. As explained at the beginning of the log we are updating, when Dawn was tested for its stability at 50 rpm, it was better balanced than had been expected. That meant it was not necessary to add as much mass to it as had been considered possible, so Dawn's final mass was less than anticipated. By then, it would have been too time consuming to update the Delta's computer parameters, so ballast masses were installed on the third stage. This brought the combined third stage and spacecraft mass to the value used in all the trajectory calculations.

With the delay in the launch and the need to redesign the guidance program for the different launch conditions anyway, engineers were able to take advantage of their knowledge of the final spacecraft mass. So the 5.34 kg (11 pounds 12 ounces) of ballast were removed from the third stage, and the new plan benefits a little from the lower mass by commanding the rocket to impart slightly more energy to the spacecraft.

A nice example of how dependent the mission is on the precise spacecraft mass.


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#53 2007-09-22 06:03:22

cIclops
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Re: Dawn - Vesta & Ceres orbiter

07pd2517-m.jpg
Fairing being secured to the Delta II upper stage booster - imaged 20 Sep 2007


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#54 2007-09-27 13:21:38

cIclops
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Re: Dawn - Vesta & Ceres orbiter

Enroute to Shed Light on Asteroid Belt - 27 Sep 2007

CAPE CANAVERAL, Fla. - NASA's Dawn spacecraft is on its way to study a pair of asteroids after lifting off Thursday from the Cape Canaveral Air Force Station at 7:34 a.m. EDT.

Mission controllers at NASA's Jet Propulsion Laboratory (JPL), Pasadena, Calif., received telemetry on schedule at 9:44 a.m. indicating Dawn had achieved proper orientation in space and its massive solar array was generating power from the sun.

"Dawn has risen, and the spacecraft is healthy," said the mission's project manager Keyur Patel of JPL. "About this time tomorrow [Friday morning], we will have passed the moon's orbit."

During the next 80 days, spacecraft controllers will test and calibrate the myriad of spacecraft systems and subsystems, ensuring Dawn is ready for the long journey ahead.

"Dawn will travel back in time by probing deep into the asteroid belt," said Dawn Principal Investigator Christopher Russell, University of California, Los Angeles. "This is a moment the space science community has been waiting for since interplanetary spaceflight became possible."

Dawn's 3-billion-mile odyssey includes exploration of asteroid Vesta in 2011 and the dwarf planet Ceres in 2015. These two icons of the asteroid belt have been witness to much of our solar system's history. By using Dawn's instruments to study both asteroids, scientists more accurately can compare and contrast the two. Dawn's science instrument suite will measure elemental and mineral composition, shape, surface topography, tectonic history, and it will seek water-bearing minerals. In addition, the Dawn spacecraft and how it orbits Vesta and Ceres will be used to measure the celestial bodies' masses and gravity fields.

The spacecraft's engines use a unique, hyper-efficient system called ion propulsion, which uses electricity to ionize xenon to generate thrust. The 12-inch-wide ion thrusters provide less power than conventional engines but can maintain thrust for months at a time.


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#55 2007-09-27 15:35:52

cIclops
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Re: Dawn - Vesta & Ceres orbiter

sept_07_trajec.jpg


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#56 2007-10-02 12:38:15

RedStreak
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From: Illinois
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Posts: 541

Re: Dawn - Vesta & Ceres orbiter

The delayed launch actually improves some things for Dawn:

1) Mars fly-by happens a month earlier.  I don't suppose anyone knows yet if Dawn has a science campaign for Mars?

2) Vesta arrival happens a little sooner, which allows for more science that'd otherwise be limited at this major asteroid.  big_smile

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#57 2007-10-07 21:33:59

EuroLauncher
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From: Europe
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Re: Dawn - Vesta & Ceres orbiter

1) Mars fly-by happens a month earlier.  I don't suppose anyone knows yet if Dawn has a science campaign for Mars?

I haven't heard anything, but I assume it will take a few Snapshots to calibrate during the fly by like the Mariners or Rosetta did. A few snapshots are going to add much about our understanding of Mars because it has many orbiters already mapping the surface.

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#58 2007-10-14 09:45:26

cIclops
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Re: Dawn - Vesta & Ceres orbiter

Joining an elite club among spacecraft, Dawn successfully fired up its xenon ion propulsion system on October 6. This important milestone in Dawn's 80-day checkout phase followed ongoing work by the mission operations team members to become accustomed to flying this new spacecraft, as they continue monitoring telemetry, adjusting onboard parameters, and conducting special activities to keep the spacecraft performing smoothly.

more ...


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#59 2007-10-25 07:56:28

EuroLauncher
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From: Europe
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Re: Dawn - Vesta & Ceres orbiter

Great news, another 3 billion miles to go ! A fly-by of II Pallas might be possible but I haven't read anything form NASA or JPL on this.

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#60 2008-01-25 03:30:09

cIclops
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Re: Dawn - Vesta & Ceres orbiter

Mission Status 8 Oct 2007 - 2 Jan 2008

January 2, 2008
Dawn has continued thrusting with its ion propulsion system since December 17. Following programmed instructions, it interrupted thrusting on December 26 and on January 2 to point its main antenna to Earth to report on its status. All systems are performing well. Now that Dawn is in interplanetary cruise, these updates will occur less frequently.

Interplanetary Cruise Begins
December 17 - 21
With the successful completion of the initial checkout phase of its mission, Dawn began the interplanetary cruise phase. While other activities will be conducted occasionally, the project's focus now is on thrusting with the ion propulsion system to reach asteroid Vesta (and later dwarf planet, Ceres).

More Instrument Tests Completed
December 10 - 14
The backup science camera was powered on for the first time this week and verified to be healthy and operating well. The primary science camera and the visible and infrared spectrometer completed additional
tests, and both instruments continue to perform extremely well.

Additional Camera Tests and Software Loads Completed
December 3 - 7
The primary science camera was operated again, acquiring images of stars as a further test of its performance. All indications are that it is operating excellently. Software that had been uploaded earlier in the mission continues to work well, so the same software was loaded this week into some of the backup locations.

Updated Software Loaded in Main Computer
November 26 - 30
This week was devoted to updating the software on the main spacecraft computer. This was planned before launch. Files were transmitted to the spacecraft, computer memory was checked, and other activities were conducted on Monday and Tuesday in preparation for rebooting the computer on Wednesday to start using the new software. On Tuesday night, the computer rebooted on its own. All diagnostic information has been returned from the spacecraft and the event is being investigated. With the new software operating as expected, controllers have verified that the spacecraft is healthy and activities are proceeding as scheduled.

Main Antenna Checked Out and New Software Uploaded
November 19 - 23
This week, the spacecraft was commanded to use its main antenna for the first time and measurements showed that it is in fine condition. New software was installed in one of Dawn's computers (and its backup), correcting a minor bug that was discovered shortly after launch.

More Ion Thrusting Tests Completed
November 12 - 16
The week-long systems test of interplanetary cruise thrusting completed successfully on Monday. The third ion thruster was tested this week, and like the other two, it performed perfectly. The thruster operated
at 4 throttle levels, including full power. In a separate activity, the mission operations team powered off the reaction wheels to test pointing control with hydrazine thrusters during ion thrusting.

Dawn Begins Cruise Thrust Test
November 5 - 9
To test the readiness of all systems for the interplanetary cruise phase of the mission (planned to begin in mid-December), Dawn is conducting a one-week execution of all the activities that will be typical of a week in that phase. As most of the time will be spent thrusting with the ion propulsion system, the spacecraft began thrusting on Monday and now has thrust for 4 days without interruption.

More Checkouts Completed
October 29 - November 2
The operations team conducted tests of special modes of the attitude control system while the ion propulsion system is thrusting. All tests showed excellent performance. Two of the three ion thrusters have been fully checked out. Tests began with the third thruster this week, and all were completed successfully. The device that emits electrons to ionize xenon was heated to drive off contaminants, and then the thruster ionized xenon (but was not commanded to accelerate it). In addition, the gimbal system that points the thruster in the required direction was operated for the first time in flight. The first test of thrusting with this thruster is not scheduled to occur until after other spacecraft tests are completed.

Second Ion Thruster Checkout Completed Successfully
October 22 - 26
The mission operations team completed the checkout of a second ion thruster this week. In one of the tests, the thruster was operated for 27 hours continuously at 5 different throttle levels, and in two other tests it was operated at maximum power for 4 hours each time. All spacecraft systems performed extremely well.

Science Instruments Checked Out
October 15 - 19
Dawn's science instruments were powered on and given their first health checks this week. The gamma ray and neutron spectrometer, imaging camera, and visible and infrared mapping spectrometer all operated
perfectly.

Ion Propulsion System Testing Continued
October 8 - 12
The ion propulsion system performed extremely well as Dawn operated two of its three ion thrusters this week. Testing of the second thruster included placing the spacecraft in an orientation in which sunlight gradually warmed some other components more than mission controllers wanted, and the spacecraft was commanded to end the activity early. The spacecraft remained healthy throughout.

Initial checkout complete with all three ion drives, science and comms  tested. On to Mars!


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#61 2008-01-26 15:01:03

Terraformer
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From: Lancashire
Registered: 2007-08-27
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Re: Dawn - Vesta & Ceres orbiter

Interplanetary travel is soooo sloooooooooooow. And 7-8 years to get to Ceres is quick? I intend to get there by 2010 at least.

That aside, I'll be watching this carefully. Ceres is my favourite planet. Speaking of which, you might want to change the title.


"I guarantee you that at some point, everything's going to go south on you, and you're going to say, 'This is it, this is how I end.' Now you can either accept that, or you can get to work." - Mark Watney

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#62 2008-01-26 16:10:01

cIclops
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Re: Dawn - Vesta & Ceres orbiter

change the title?


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#63 2008-01-27 07:07:57

Terraformer
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From: Lancashire
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Re: Dawn - Vesta & Ceres orbiter

It currently says Ceres is an asteroid.


"I guarantee you that at some point, everything's going to go south on you, and you're going to say, 'This is it, this is how I end.' Now you can either accept that, or you can get to work." - Mark Watney

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#64 2008-01-27 09:53:12

cIclops
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Registered: 2005-06-16
Posts: 3,230

Re: Dawn - Vesta & Ceres orbiter

Right smile


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#65 2008-01-27 10:46:57

RedStreak
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From: Illinois
Registered: 2006-05-12
Posts: 541

Re: Dawn - Vesta & Ceres orbiter

It currently says Ceres is an asteroid.

"Dwarf Planet" btw, not "Planet" if you go by the IAU's somewhat lame nomenclature to amend Eris and Pluto.  roll

Hold off on calling Ceres even Dwarf Planet for a bit...more than likely they'll redefine what the heck to call Pluto, Eris, et. al. within a few years.  Gez...you'd think the astronomical community was more creative than 'dwarf planet'.

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#66 2008-01-27 12:24:20

cIclops
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Re: Dawn - Vesta & Ceres orbiter

To avoid such problems, the title is now changed to Ceres smile


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#67 2008-02-06 03:19:50

cIclops
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Registered: 2005-06-16
Posts: 3,230

Re: Dawn - Vesta & Ceres orbiter

Dawn Journal by Marc Rayman - 31 Jan 2008

The spacecraft has accumulated more than 1000 hours of thrusting with its ion propulsion system. Although far, far longer than the overwhelming majority of spacecraft have operated their propulsion systems, this represents only a small fraction of the total thrusting required to complete its solar system journey.

Dawn is 67 million kilometers (42 million miles) from Earth or 175 times as far as the moon. Radio signals, traveling at the universal limit of the speed of light, take more than 7.5 minutes to make the round trip.

Note also second software reset event on 14 Jan 2008.


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#68 2008-05-06 00:50:09

cIclops
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Registered: 2005-06-16
Posts: 3,230

Re: Dawn - Vesta & Ceres orbiter

Dawn Journal update - 22 Apr 2008

Dawn continues its powered flight, having accumulated more than 100 days of ion thrusting since its launch nearly 7 months ago. All systems are healthy as the probe patiently and persistently propels itself through the solar system.

In addition to its weekly hiatus in thrusting to point its main antenna to Earth for about 6 hours, Dawn's flight plan includes occasional longer intervals to conduct special activities. On March 31, the spacecraft stopped its ion beam, turned to Earth, reported on its activities from the previous week, and indicated its readiness (even eagerness!) for whatever plans mission control had devised. This period, scheduled well before launch, was planned to last 10 days.

To begin, the team loaded into the spacecraft's main computer updated software that simplifies operation of the science instruments. Such "science blocks" had already been used in the mission, but with the experience gained from the tests of the instruments in the initial checkout phase, the team made some improvements. After thorough testing with instrument simulators, the modified science blocks had been deemed ready for installation on the spacecraft. They were used during the rest of the week, as each of Dawn's science instruments received special attention.

(more)


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#69 2012-03-29 05:35:25

LittleGreenMen
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Registered: 2012-03-29
Posts: 1

Re: Dawn - Vesta & Ceres orbiter

*beep*

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#70 2014-01-23 17:29:03

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 15,597

Re: Dawn - Vesta & Ceres orbiter

There has been word of gyser like water being seen from the Herchell telescope and others.
Why is this just now happening as I do not believe we hhave seen this happen before? Is there any connection to the Mars event.

spacetodat.net

European spacecraft detects water vapor around Ceres
Posted: Thu, Jan 23 7:40 AM ET (1240 GMT)

Astronomers analyzing data from a European space telescope say they have discovered water vapor in the vicinity of the dwarf planet Ceres. European scientists said observations of Ceres by the infrared space telescope Herschel detected water vapor in the vicinity of the world, the largest body in the main asteroid belt between Mars and Jupiter. Astronomers said the water vapor appeared to be emanating from just two locations on Ceres's surface that are slightly darker and warmer than the rest of the surface. Scientists said they didn't know if water vapor came from the sublimation of ice located near the surface or deeper inside the dwarf planet. NASA's Dawn spacecraft will study these regions in further detail when it enters orbit around Ceres early next year.

Last edited by SpaceNut (2014-01-23 17:34:27)

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#71 2014-01-24 00:16:31

RGClark
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From: Philadelphia, PA
Registered: 2006-07-05
Posts: 501
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Re: Dawn - Vesta & Ceres orbiter

SpaceNut wrote:

There has been word of gyser like water being seen from the Herchell telescope and others.
Why is this just now happening as I do not believe we hhave seen this happen before? Is there any connection to the Mars event.

spacetodat.net

European spacecraft detects water vapor around Ceres
Posted: Thu, Jan 23 7:40 AM ET (1240 GMT)

Astronomers analyzing data from a European space telescope say they have discovered water vapor in the vicinity of the dwarf planet Ceres. European scientists said observations of Ceres by the infrared space telescope Herschel detected water vapor in the vicinity of the world, the largest body in the main asteroid belt between Mars and Jupiter. Astronomers said the water vapor appeared to be emanating from just two locations on Ceres's surface that are slightly darker and warmer than the rest of the surface. Scientists said they didn't know if water vapor came from the sublimation of ice located near the surface or deeper inside the dwarf planet. NASA's Dawn spacecraft will study these regions in further detail when it enters orbit around Ceres early next year.


Geysers have just recently been observed from the Jovian moon Europa, and for a few years now from the Saturnian moon Enceladus. Geysers have been deduced to be occurring on the polar regions of Mars because of the presence of fan-shaped deposits there, but they have not yet been observed directly.
I discuss the Martian geysers here:

Index» Unmanned probes» Public recruited to identify geysers on Mars.
http://newmars.com/forums/viewtopic.php?id=6878

  Bob Clark


Nanotechnology now can produce the space elevator and private orbital launchers. It now also makes possible the long desired 'flying cars'. This crowdfunding campaign is to prove it:
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#72 2014-01-24 09:53:27

Tom Kalbfus
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Re: Dawn - Vesta & Ceres orbiter

The question is what would cause a geyser on Ceres? Ceres isn't subject to the same tidal stresses as Enceladus is.

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#73 2014-01-24 11:21:28

Void
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Registered: 2011-12-29
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Re: Dawn - Vesta & Ceres orbiter

It most likely is just exposed ice evaporating.

But as a long shot, I have speculated that the solar wind having magnetic properties and fluctuating could cause molecules to be nudged a bit.

Either ferous materials, or salt water pockets.  I've only gotten silence so far on that suggestion when I have ever brought it up.

Even on Earth, with a protective magnetic field, enormous energies are exhibited during large solar storms.  So much as to knock out power grids.

It could generate heat by nudging molecules, and also, could also generate large ground currents with counter EMF.

Last edited by Void (2014-01-24 11:23:55)


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#74 2014-01-24 13:10:09

Terraformer
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Re: Dawn - Vesta & Ceres orbiter

There isn't really any surface pressure on Ceres. If there's an ocean under the ice, and the ice gets thin enough, it's easy to see how an explosion could occur (if the water is warm enough).


"I guarantee you that at some point, everything's going to go south on you, and you're going to say, 'This is it, this is how I end.' Now you can either accept that, or you can get to work." - Mark Watney

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#75 2014-01-24 14:44:23

GW Johnson
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From: McGregor, Texas USA
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Re: Dawn - Vesta & Ceres orbiter

It's my understanding that Ceres has no atmosphere,  and a very low surface gravity.  For there to be geysers,  there has to be liquid water inside there somewhere. 

Liquid water requires sufficient water vapor partial pressure (or its equivalent) over the liquid surface to be stable,  a number dependent on the temperature of the liquid.  That comes right out of the standard steam tables we've used for two centuries now.  At 0 C that's 0.0060 atm.  At 37 C that's 0.062 atm.  No way around that set of physics.  If the water vapor partial pressure is too low,  the liquid is unstable and evaporates or boils away.  A violent boil down in a hole with a path to space would produce a geyser.

Without an atmosphere,  the water vapor is the atmosphere over any liquid surface.  That,  or solid cover held in place by gravity.  The overburden weight (weight,  not mass!!!!) per unit of interface area is the pressure exerted upon the liquid by the solid overburden.  This could be ice or it could be dirt,  or a mixture of both.  Disturb the ice or dirt,  and the liquid or ice below it evaporates away.  We've already seen this on Mars where the rovers dig and hit buried ice.

If there's liquid water inside Ceres,  anything that produces cracking or any other disturbance to the overburden then opens up a path to space.  The water will boil violently away into vacuum until (1) it is gone,  or (2) ice and debris plug the path to space.  The observed geysers testify to (1) the presence of liquid water,  and (2) some sort of overburden disturbance that opens up a path to space. 

Assuming that ice and debris plug the path to space.  If the plug is not stable over geologic time,  it would open and close repeatedly,  and perhaps at irregular intervals.  There's a mechanism for repeated geyser eruptions. 

The disturbance that sets this off could be as simple as surface impacts of other bodies.  Another possibility is some kind of an "earthquake".  (Not much of a word choice here.)

The presence of liquid water demands a heat source to keep it from freezing over geologic time.  There not being a big planet nearby,  unsteady gravitational stress seems an unlikely source of the heat.  That leaves (1) radioactive decay,  (2) something electromagnetic perhaps from the sun,  or (3) something we are not yet aware of.  All three are intriguing possibilities. 

If it were radioactive decay,  that heat source would have been far stronger in the geologic past.  That poses some problems with why Ceres is what it is today.  But,  who knows?

I hope the probe can help sort all this out.  I doubt they had things like this in mind when they designed it.

GW


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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