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Dawn at Ceres: ‘Down Among Them’

The new images just in from Dawn at Ceres unexpectedly evoke a much earlier mission, the Apollo 10 precursor to the lunar landing. This was the second manned mission to orbit the Moon, one that saw the lunar module drop to just over 15 kilometers from the surface in a rehearsal for the Apollo 11 landing. Just for fun, I’ve been looking through the Apollo 10 transcripts for day 5, when the LM (‘Snoopy’) had already separated from the command module.

John Young was in the command module as Gene Cernan and Tom Stafford put Snoopy through its paces. Nobody had ever been this close to the Moon before. You probably remember or else have read about Snoopy’s descent toward the lunar peaks:

100:25:43 Young: …at 6 miles, he was doing 65 feet a second (20 m/s) on my – 6 miles (9.6 km) from me, he was doing 65 feet per second (20 m/s). At 3.8 miles (6.1 km) he was doing 73 feet per second (22 m/s). I think that confirms this burn. They are down there among the rocks…

As Cernan quickly confirmed:

100:26:54 Cernan (in Snoopy): We is Go, and we is down among them, Charlie.

To which capcom Charlie Duke in Houston replied:

100:26:57 Duke: Roger. I hear you weaving your way up the freeway. Can you give me a post-burn report? Over.

And later:

100:44:57 Cernan (in Snoopy): Hey, I tell you, we are low! We are close, babe! This is, like, it! And it really looks pretty smooth down there, surprisingly enough.

Dawn is not a manned mission, but I couldn’t help thinking of those Apollo 10 moments (still vivid in my memory) when I looked at the latest imagery from Ceres. The spacecraft has now descended into its final and lowest orbit at the dwarf planet, which will bring us the highest resolution images we’ll get. Here we are ‘down among them,’ though not nearly as close as Apollo 10 to the Moon. The altitude is approximately 385 kilometers, an altitude that Dawn will maintain for the rest of the mission. The resolution in the image below is 35 meters per pixel.


Image: This image of Ceres was taken in Dawn’s low-altitude mapping orbit around a crater chain called Gerber Catena. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA.

Ceres is a small world, a mere 940 kilometers in diameter, but the trough features are interesting, a common sight on larger planets. They are thought to be the result of impact stresses and contraction, and as this JPL news release points out, may also result from the loading of the crust by large mountains (think Olympus Mons on Mars). Researchers believe similar processes have occurred across Ceres, with some troughs possibly reflecting internal tectonic stresses. “Why they are so prominent is not yet understood,” says Paul Schenk (Lunar and Planetary Institute) but they are probably related to the complex crustal structure of Ceres.”

So bit by bit, we’re working out Ceres’ mysteries. We’ve recently learned that the bright material found in craters like Occator is consistent with hexahydrite, which is a type of magnesium sulfate (see Catching Up with Dawn at Ceres). We’ve also learned that Ceres contains ammoniated clays, which leads to the speculation that it may have formed as far out as the orbit of Neptune and migrated inward, or else later drew in materials that formed there.

We have months of data and imagery ahead. With Dawn’s primary and backup framing cameras both operational, we turn to the craft’s visible and infrared mapping spectrometer, which will identify minerals by analyzing the wavelengths of light reflected off the surface. The abundance of various elements will be measured by the craft’s gamma ray and neutron detector (GRaND). And after operations have ended? Dawn was able to leave Vesta but it will never leave Ceres, its orbit stable enough that it will remain as a satellite of the dwarf planet.

Sometimes I have to remind myself that what I am looking at is real, given that Ceres has been no more than an blurry speck for most of my life. Spaceflight kicks off the grandest of enthusiasms, infusing us with genuine wonder even when we’re in the most demanding of situations. On that note I return briefly to Apollo 10, at the moment during the LM’s descent when the Earth began to rise and highly trained astronauts gave voice to the moment:

100:25:30 Cernan (in Snoopy): Look at that – look at the Earth! Look at the Earth!

[Very excited comments at seeing Earthrise.]

100:25:33 Stafford (in Snoopy): Oh gee. Look at the Earth, John. Get it, get it.

100:25:42 Stafford (in Snoopy): Oh my God, I can’t believe it! It’s just…

I wouldn’t have been able to find the words either. Here’s the image from Snoopy.

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Comments on this entry are closed.

  • Michael December 23, 2015, 13:54

    Still looks like mini moon to me!

    It looks very dusty that why I think the bright spots are a lot, lot younger than the original impact craters. I would have thought less than a million years!

    We need a rover here for sure.

  • Alex Tolley December 23, 2015, 15:28

    I could live with penetrators to expose the subsurface material for analysis by spectroscopy and by physical capture of the ejecta, as well as permanent seismometers as part of mission. Before the encounter, I was expecting Ceres to be an icy snowball, possibly differentiated, rather like a very large comet. I should have guessed it was going to be a lot more interesting than that.

    On a much broader scale, we are getting just the sketchiest idea of exoplanets. In due course they will be much more interesting, and an eventual high resolution image or even probe to a nearer one will make them rich and interesting worlds too.

    Do we know how long Dawn will operate for? Will we be able to get long term data about its surface rather than just the encounter period snapshot?

  • Steven Torry Rappolee December 23, 2015, 17:16

    Snoopy is thought to be in solar orbit,


  • Steven Torry Rappolee December 23, 2015, 17:21

    And another Snoopy astrodynamics article


  • J. Jason Wentworth December 23, 2015, 22:56

    We *should* link the Moon and Ceres in our thinking about solar system exploration, settlement, and utilization, because all three activities are excellent reasons to establish a Moon base. Here’s why:

    With even a modest, Antarctica-type Moon base equipped with a “lunatron” (an electromagnetic launching track of the type that Arthur C. Clarke proposed in a 1950 JBIS paper and popularized in his 1962 short story “Maelstrom II”; that same year William Escher of the NASA Marshall Space Flight Center produced an engineering study of the concept and coined its name), Ceres would be quite easy to reach, and to return from–and a similar launcher on Ceres would be even more attractive due to the still-lower gravity there. Also:

    Such launchers would enable spacecraft (including piloted ones), self-guided cargo containers, and containers of locally-produced rocket propellants (even cryogenic ones–long-term storage insulation for the tanks is feasible since rocket mass ratios are not involved in accelerating them to the local escape velocity–tugs from their destinations or onboard electric thrusters could bring them to their destinations at low relative velocities) to be dispatched anywhere in the solar system, without consuming vast quantities of rocket propellant. Closer to home, a lunatron would enable refueling of Earth-orbiting satellites and spacecraft much more cheaply than could be done from Earth. It could also launch spacecraft and cargo into orbit around the Moon cheaply (to resupply lunar orbit or Earth/Moon Lagrange point space stations, for example), requiring just a small orbit circularization burn at apolune (also called apocynthion). In addition:

    While Arthur C. Clarke proposed these ideas in “The Promise of Space,” Neil P. Ruzic covered them in detail in his lunar settlement advocacy books “Where the Winds Sleep” and “The Case For Going to the Moon.” Ruzic’s lunatron launchers were quite simple, consisting of linear “lunar cryostats” (he obtained a patent for this very simple, stacked aluminized mylar deep-cold vacuum device) that would utilize superconductivity during the two-week lunar night to levitate the spacecraft or other projectile just above the track (he also designed a high-speed lunar surface transportation network that would use these levitation belts, as he called them), using push-pull electromagnets to accelerate the spacecraft to launch velocity.

  • Larry Kennedy December 24, 2015, 7:28

    A lot in this little post. Does a good job of tieing the old with the new. Thanks for once again reminding me that I have been lucky enough to live through some incredible times, and with steadily improving communication technology have been able to experience it in amazing detail.

  • Michael December 30, 2015, 4:30

    I am wondering just how hard it would be to move through that dust on Ceres’s surface with such a low gravity field, it could be quite easy, perhaps a swimbot could be used as well.

  • Alex Tolley December 30, 2015, 12:42

    @Michael – it is a pity Philae’s harpoons didn’t deploy on 67P/C-G failed, or we may have had one answer to this. That the lander bounced at ~ 1/3 m/s suggests that the surface was fairly compacted.

    There is also some hints based on the “touchdown” on Eros, the sample return from Itokawa, and possibly the deep impact sampling of comet Temple 1.