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Dawn Orbits Ceres

I spent the morning working on an interesting paper about detecting ‘exorings’ — ring systems like Saturn’s around exoplanets — while switching back and forth to Twitter and various Web sources to follow events as the Dawn spacecraft became gravitationally captured by Ceres. I have problems with so-called ‘multi-tasking,’ which at least in my case means I do two things at once, performing each task less effectively than if I were tackling them separately. Fortunately, I have all weekend to tune up the exorings story, and I put it temporarily aside to work on Dawn’s historic arrival.

Congratulations to the entire Dawn team on the continuance of this splendid mission. We have much to look forward to as observations proceed and the orbit stabilizes. Similarly, we have the almost immediate prospect of following New Horizons in to Pluto/Charon, another case of a previously blurry object taking on breathtaking resolution as the days pass. The bounty of 2015 then opens into an uncertain future when it comes to exploring the outer system, but we can hope that the New Horizons extended mission will happen as anticipated and investigate a Kuiper Belt Object. We can also hope that the European Space Agency proceeds with its Jupiter Icy Moons Explorer without what would have been the NASA side of the mission.

Regarding Dawn, remember that the benefits of ion propulsion have never been more obvious thanks to this mission. The first spacecraft to reach orbit around a dwarf planet (at approximately 1239 UTC today), Dawn is also the first spacecraft to orbit more than one target, having explored the asteroid Vesta from 2011 to 2012 before moving on to its current location. That gives us quality data time at the two most massive asteroids in the main belt that stretches between Mars and Jupiter.


The just released image above was taken on March 1, before orbital insertion and before Dawn swung behind Ceres. The view is just a teaser for the scenery we’re going to be looking at as the spacecraft begins its orbital investigations. It took seven and a half years to get here (and 4.9 billion kilometers along the route), but we now have a healthy spacecraft at its target. This image was taken about 48,000 kilometers out, at a Sun-Ceres-spacecraft angle (phase angle) of 123 degrees. The image scale here is 2.9 kilometers per pixel. We’ll get new imagery in April as Dawn moves back around the near side of Ceres with respect to the Sun.


Comments on this entry are closed.

  • Harry R Ray March 6, 2015, 14:28

    Now that Dawn has achieved orbit, it’s time for me to enter the “What Celestial Object does Ceres remind you the most of” sweepstakes (any other takers). To me, it’s a simple suprising answer: Uranus’ moon, Umbriel. Outside of being just a little bit larger than Ceres, Umbriel has the same low albedo (surprising, because all of the other Uranian moons have much higher albedos),the same “relaxed” craters, and, MOST IMPORTANTLY, the same mysterious white spots. Refresh your memory and “google” Umbriel. Remember the wierd “doughnut” near Umbriel’ s equater (also remember that you are observing Umbriel nearly pole-on, to the “doughnut appears at the very top of the image)

  • Christopher L. Bennett March 6, 2015, 14:42

    Yay, Ceres orbit!

    Or as I like to call it, a Ceres circuit. :D

    Seriously, I look forward to what we discover, and I hope it doesn’t contradict my novel ONLY SUPERHUMAN too badly. But I did include the following line in the book:

    “The sunlit side of the dwarf planet was a dusty gray, except for the bright glints where craters or mining operations had exposed fresh ice beneath.”

    So far, so good… Well, depending on what the bright spots turn out to be.

  • ljk March 6, 2015, 14:46
  • Brett March 6, 2015, 15:05

    I can’t wait for them to finally get some good images of the White Spots. Cryovulcanism or impact-exposed terrain? We should take up bets.

  • Michael March 6, 2015, 15:33

    Still looks like mini moon to me! Now I and countless others have waited ages for this encounter, finally we can have some in depth science to work out how the solar system formed and importantly where Jupiter went during its formative years. Remember Jupiter is the 800lb gorilla and where it went it held a large sway over the rest of the formation of the Solar system.

    Start building those rovers NASA!

  • Andrew Palfreyman March 6, 2015, 15:57

    3D manoevres to Ceres orbit for Dawn.

  • Lionel Ward March 7, 2015, 12:49

    Great writing Paul.

    @ljk, really like the NASA videos made by the Dawn team that were on the PS blog – pleased to see NASA making good efforts with publicity

    @Michael, here’s to a Ceres rover! I wonder what would be achievable now that the Falcon Heavy and SLS are on their way. MSL was launched on an Atlas V 541 which has just a third of the payload to LEO which the Falcon Heavy will have.

  • Wojciech J March 8, 2015, 11:21

    Michael and Lionel-China is studying a mission concept involving Ceres sample retrieval. It is still a concept and we will see what comes out of it. With NASA’s limited budget it is good to know that it is not on its own in exploration of space.

  • Joy March 8, 2015, 16:43

    Kudos to JPL and Marc Rayman! Considering Deep Space 1 and Hayabusa were also successful, that makes a hat trick for ion propulsion! Hayabusa 2 is already outbound for a second asteroid sample return mission, to arrive at the target in July 2018. So we have something to look forward to 3 years after the Pluto flyby. After that… what?

    I would like to see Russia have a go at a Fobos-Grunt sample return mission again. But seeing as the neocon entourage of the demented Galician Nazi nobleman, Zbigniew Brzezinski, is hell-bent on starting WWIII – Russia has other problems to deal with at the moment.

  • Ashley Baldwin March 8, 2015, 17:19

    A small, unremarkable ball of rock and ice at first glance but how misleading first impressions can be at first glance. One of the darkest objects in the solar system. Why? A planet that didn’t make it thanks to the complex dynamic interactions of the early solar system and especially “Jumping Jupiter” . What is its Deuterium:Hydrogen ratio and how does that compare with Earth’s water? And how is it so different from bone dry and older Vesta? That’s before we even get to see it up close and personal and see what those two bright spots are. I can’t see how they are due to any form of cryovulcanism but stranger things have been known to happen. As with Pluto, it’s great to see these ancient specks of light become discernible worlds with unique geography ,geology and chemistry .

  • John March 9, 2015, 17:45

    I’m still keeping all those medels that predicted Ceres would’ve had an internal ocean for a billion years after it formed – it may be an ice ball today, but I’m expecting that its surface will show signs of it having been a very different world in the deep past!

  • Eniac March 15, 2015, 0:30

    Joy: I am starting to suspect that you get some of your more ideosyncratic views from places such as this: http://www.rense.com/general81/abig.htm. Stay away from the deep end….

  • ljk April 13, 2015, 13:12
  • ljk April 16, 2015, 18:56

    Images released of the north pole of Ceres:


  • ljk June 1, 2015, 8:16

    Dawn Journal: Spiralling Closer to Ceres

    Posted by Marc Rayman

    2015/05/29 12:32 UTC

    Dear Emboldawned Readers,

    A bold adventurer from Earth is gracefully soaring over an exotic world of rock and ice far, far away. Having already obtained a treasure trove from its first mapping orbit, Dawn is now seeking even greater riches at dwarf planet Ceres as it maneuvers to its second orbit.

    The first intensive mapping campaign was extremely productive. As the spacecraft circled 8,400 miles (13,600 kilometers) above the alien terrain, one orbit around Ceres took 15 days. During its single revolution, the probe observed its new home on five occasions from April 24 to May 8. When Dawn was flying over the night side (still high enough that it was in sunlight even when the ground below was in darkness), it looked first at the illuminated crescent of the southern hemisphere and later at the northern hemisphere.

    When Dawn traveled over the sunlit side, it watched the northern hemisphere, then the equatorial regions, and finally the southern hemisphere as Ceres rotated beneath it each time. One Cerean day, the time it takes the globe to turn once on its axis, is about nine hours, much shorter than the time needed for the spacecraft to loop around its orbit. So it was almost as if Dawn hovered in place, moving only slightly as it peered down, and its instruments could record all of the sights as they paraded by.

    Full article here:


    To quote:

    “To gain the same view Dawn had, simply build your own ion-propelled spaceship, voyage deep into the main asteroid belt between Mars and Jupiter, take up residence at the giant orb and look out the window. Or go to the image gallery here:”



    After having been viewed as little more than a smudge in telescopes for more than two centuries since its discovery, Ceres now is seen as a detailed, three-dimensional world. As promised, measurements from Dawn have revised the size to be about 599 miles (963 kilometers) across at the equator. Like Earth and other planets, Ceres is oblate, or slightly wider at the equator than from pole to pole. The polar diameter is 554 miles (891 kilometers). These dimensions are impressively close to what astronomers had determined from telescopic observations and confirm Ceres to be the colossus we have described.

    Before Dawn, scientists had estimated Ceres’ mass to be 1.04 billion billion tons (947 billion billion kilograms). Now it is measured to be 1.03 billion billion tons (939 billion billion kilograms), well within the previous margin of error. It is an impressive demonstration of the success of science that astronomers had been able to determine the heft of that point of light so accurately. Nevertheless, even this small change of less than one percent is important for planning the rest of Dawn’s mission as it orbits closer and closer, feeling the gravitational tug ever more strongly.