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Probing the Surface of Ceres

It doesn’t stretch credulity to hypothesize that the early Earth benefited from an influx of comet and asteroid material that contributed water and organic compounds to its composition. The surface of a world can clearly be affected by materials from other bodies in the Solar System. Now we’re learning that the dwarf planet Ceres may have a surface dusted by material from asteroid impacts. The findings come from a team of astronomers investigating Ceres with SOFIA, the airborne Stratospheric Observatory for Infrared Astronomy. The observatory is a highly modified 747SP aircraft carrying a 2.5m reflecting telescope.

The study shows that not just Ceres but other asteroids and dwarf planets may be coated with asteroid fragments, a result that adjusts our view of Ceres’ surface composition. After all, what we’re looking at may simply be the result of asteroid impacts in the early days of the Solar System’s formation. Three quarters of all asteroids, including Ceres, have been classified as type C (carbonaceous) on the basis of their colors, but the SOFIA infrared data show a substantial difference between the dwarf planet and C-type asteroids in nearby orbits.

Carbonaceous asteroids are dark (albedo in the range of 0.03-0.09, on a scale where a white, perfectly reflecting surface has an albedo of 1.0), with a composition depleted in hydrogen, helium and other volatiles. What SOFIA shows us is that Ceres doesn’t fit this model. Pierre Vernazza is a research scientist at the Laboratoire d’Astrophysique de Marseille:

“By analyzing the spectral properties of Ceres we have detected a layer of fine particles of a dry silicate called pyroxene. Models of Ceres based on data collected by NASA’s Dawn as well as ground-based telescopes indicated substantial amounts of water-bearing minerals such as clays and carbonates. Only the mid-infrared observations made using SOFIA were able to show that both types of material are present on the surface of Ceres.”

Observations of ceres

Image: Ceres’ surface is contaminated by a significant amount of dry material while the area below the crust contains essentially water-bearing materials. The mid-infrared observations revealed the presence of dry pyroxene on the surface probably coming from interplanetary dust particles. The Internal structure of the Dwarf Planet Ceres was derived from NASA Dawn spacecraft data. Credit: SETI Institute.

Interplanetary dust particles, according to this SETI Institute news release, are the most likely source for the pyroxene, and are also implicated as having accumulated on other asteroid surfaces. Ceres thus takes on the coloration of some of its drier neighbors, while actually housing more substantial resources of water below. The larger picture is that infrared observations may help us better understand an asteroid’s true composition. Vernazza even speculates that ammoniated clays mixing with watery clay on Ceres may point to an origin in the outer parts of the Solar System, with migration occurring later in the dwarf planet’s life.

“The bottom line is that seeing is not believing when it comes to asteroids,” says Franck Marchis, senior planetary astronomer at the SETI Institute, a researcher who collaborated in this project. “We shouldn’t judge these objects by their covers, as it were.”

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Comments on this entry are closed.

  • Geoffrey Hillend January 24, 2017, 17:09

    What about the idea of sending astronauts there with an LEM style lander with seismic equipment to probe the interior. They could land near or inside a crater and dig beneath the surface a little way to confirm the chemistry of the interior.

    If we could get a more powerful power plant for VASIMR and make an interplanetary space vehicle which was fast, they could go there. NASA is always taking about the deep space exploration with astronauts. It might be an easy mission due to low gravity and no atmosphere of Ceres.

    • Jens Knudsen January 26, 2017, 15:02

      A radio controlled digger and driller. :)#

  • Geoffrey Hillend January 24, 2017, 17:14

    A small unmanned lander or rover might be a cheaper alternative.

  • Marshall Eubanks January 24, 2017, 19:20

    It’s a bit harder to get to than Mars, but much easier to land once you are there. I can’t see anything like that happening with a crewed mission until well after the first Mars landing. Even an automatic lander would probably not fit in a Discovery cost cap, which means that it would be a decade at least before it could get approved.

  • Phil January 26, 2017, 3:17

    “Even an automatic lander would probably not fit in a Discovery cost cap”

    Are we all certain about that? Pathfinder was a Discovery class mission that had to deal with Mars EDL and it had a rover. Admittedly it also had a useful orbiter to use as a relay. Solar panels have improved in the last 20 years. Ideas? Hard penetrators maybe?

    P

    • Michael January 28, 2017, 2:41

      We might be able to use a solid rocket (concertina design) as the decent and impact absorber all in one, once the rocket has fired to slow it down it then impacts the surface.

  • Harry R Ray January 26, 2017, 10:22

    Recent CONFIRMATION of water vapor AND a haze layer ABOVE Occator crater DEMANDS a MORE COSTLY MISSION! Something that can detect ORGANISMS either IN the haze layer OR on the surface. A budget something similar to Cassini would seem reasonable. If the TRUMP administration objects, the argument that the Chinese could detect life on Ceres BEFORE WE DO would probably convince them to change their minds.

  • Alex Tolley January 26, 2017, 12:59

    I would also like to know more about the interior. What can be inferred from the salt deposits? I would also like to see more information for internal structure, such as G. Hillend’s desire for seismometers to determine its structure. This surely cannot be that hard to do? Cell phones can detect seismic activity, albeit not with high sensitivity, but they are small. A decent number of seismometers placed on the surface could continue to record data from the odd inpactor, although initial data could be obtained by crashing the carrier craft into Ceres. The energy to land the seismometers is very low (Ceres escape velocity is ~0.5 km/s) so small, simple chemical rockets are adequate, as would the rocket to place the craft in orbit. A swarm of small seismometers would provide redundancy in case of the inevitable losses. The orbiter would be a long term observation platform and data relay. Whether the craft would be propelled by chemical rockets for speed, or ion engines for reduced mass, but probably longer travel time is an engineering and cost choice. Could cubesats be the platform for the seismometers?

    • Michael January 28, 2017, 10:22

      There was a design I was thinking about and that was to use instruments (very small) imbedded in a polymer sail, maybe a bubble wrap type. Once the sail hit the ground it would bounce (provided the impact velocity was not to high) and disrupt the communications but once the sail stopped the communication could resume through the transparent polymer. Having distributed electronics with no direct solid links (just optical) to the next electronic element allows us to survive very high decelerations.

  • Geoffrey Hillend January 26, 2017, 21:34

    An high gain dish antenna might be necessary for a cubesat as well as the lander? Also there might not be a lot of Earthquakes on small asteroids since the core might have cooled off or cools off faster on smaller bodies so one might have to wait for the occasion asteroid collision for seismic waves or make one’s own collision with a weight ejected from the orbiter. Ceres has ice for a mantle or crust and I wonder if there is still any heat in the core other process might trigger quakes like meteor collisions since ice has a low melting point.

  • Geoffrey Hillend January 27, 2017, 16:42

    The Mars Insight lander has a very sensitive Seismometer, but it won’t be launched unto May 5, 2018. If it a success maybe they can send something like it to Ceres or Europa.

  • Jeff Wright January 27, 2017, 17:13

    At least you don’t have to dig too deep to reach metal
    https://news.brown.edu/articles/2015/10/ceres

  • ljk February 2, 2017, 18:40
  • ljk February 2, 2017, 19:22