NASA’s Dawn Probe Has Arrived at Dwarf Planet Ceres

By Sarah Scoles | March 6, 2015 10:27 am

An artist’s concept of the Dawn spacecraft arriving at Ceres.

Today, dwarf planet Ceres became the first such planet to have company over. The visitor is NASA’s Dawn spacecraft, which reached its final destination — an orbit around this 590-mile-wide ball of ice and rock — after more than seven years in space.

And now that Dawn is finally all up on this space rock, astronomers can take sharp snapshots of its surface and learn about what makes Ceres Ceres, which they’ll do for the next 16 months. In the process, they will investigate why some planet-like objects didn’t quite grow into planets (sorry, Pluto — we’re looking at you), what the solar system was like billions of years ago, and what that tells us about Earth today.

A New Day for Dawn

NASA launched Dawn in 2007, way back when Steve Jobs first announced this crazy thing called an iPhone. It traveled for four years to arrive at Vesta, a giant asteroid, where it spun around the surface for 14 months. Then, in 2012, Dawn’s ion drive (for real) propelled it out of orbit and back on its journey.

It began its approach to Ceres in December, beaming back HD images of the dwarf planet starting in late January.

Dwarf planet Ceres seen on Feb. 19.  Credit: ASA/JPL-Caltech/UCLA/MPS/DLR/IDA

Dwarf planet Ceres seen from Dawn spacecraft on Feb. 19. Credit: ASA/JPL-Caltech/UCLA/MPS/DLR/IDA

Today, it becomes not just the first spacecraft to visit a dwarf planet but also the first spacecraft to orbit two different non-earthly objects. Guinness Book: Are you listening?

Origin Story

Sicilian astronomer Giuseppe Piazzi first saw Ceres in 1801. He called it a planet. But soon, other observers began to see more stuff like Ceres in the same region of space. That area became known as the asteroid belt, and Ceres became an asteroid. But Ceres is huge. If you spread its surface over the United States, it would cover more than one-third of the continental land.

So in 2006, at the same time that Pluto got demoted, Ceres received a promotion: both “bodies” (as astronomers call them) are now officially dwarf planets. They have enough gravity to pull themselves into spheres, but they haven’t swept up or kicked out all the debris in their orbits.

What Makes Ceres Special?

Ceres formed in the very early days of the solar system, when bits of debris were smacking into each other, sticking together, and snowballing into planets. Ceres stopped growing before it became fully fledged. But that arrested development makes Ceres a time capsule: one that shows us what the solar system used to be like, and what it was made of, back in its Wild West days.

Ceres seems to be about 25 percent water. The water on Earth had to come from somewhere. That’s not to say it came from Ceres (it didn’t), but it may have come from objects a lot like Ceres. Last year, the Herschel space telescope spotted two plumes of water shooting from the surface. Some scientists speculate that these are like the icy volcanoes on Enceladus, which means an ocean might slosh below the icy surface, but nobody knows yet. They could be the result of meteorites crashing into the surface and kicking up the ice we know is there.

Curiously, though, the plumes roughly correspond to two eerie bright spots in one of Ceres’ craters. (See top image.) That correspondence could point to coincidence, “cryovolcanoes,” crashes — or none of the above. There’s lots of speculation right now, but the whole point of Dawn is to get some cold, hard, high-res images and composition analysis.

Asteroid Ceres with twin jets of steam

Twin jets of steam were spotted coming from Ceres in late 2012, as shown in this illustration. Credit CNRS/Y Gominet, B Carry

The Coming Dawn

Dawn will tell us what those spots are, where the water came from, maybe more about where our water came from, and all about the craters pocking Ceres’ surface. NASA wants to avoid a debacle about crater naming — like the debate that ensued after a company called Uwingu asked people to pay for the privilege of christening martian craters (for the record, I named mine “Sarah’s big hole in the ground”). This time, Cerian features will be named “for gods and goddesses of agriculture and vegetation from world mythology” and “agricultural festivals.”

Even if we can’t name Ceres’ geography, Dawn will allow us to connect with Ceres in other ways. What would it be like to stand on a world that is almost — but not quite — a planet? Dawn will enlighten us.

CATEGORIZED UNDER: Space & Physics, top posts

    You know…Not all dwarf planets are the same.

  • tibet

    Ceres Lanister, oh wait, wrong kind of dwarf, never mind, wrong blog.

  • stevlich

    One thing that’s guaranteed is that NASA will never find life anywhere, just planetary and celestial features. Nobody cares about that crap anymore. Show me an Okovongo Delta on Ceres and then we’re talking. But NASA won’t even find an amoeba anywhere. Such incorrigible bastards.

    • Mike Richardson

      Why don’t you think they’d find life? They might be understandably wary about making announcements until they have something pretty concrete, considering how the Mars microbes incident in the 1990s panned out. But it is in their interest to find life — nothing would help them argue for a bigger budget.

      • stevlich

        Mike, what you say makes perfect sense but nobody ever said that NASA was logical. They’re addicted to suffering and making the public suffer by showing us boring finds that are merely bookkeeping and nothing to write home about.

        • Mike Richardson

          Well, Ceres has turned out to be more interesting than a ball of rock so far, but I guess I can understand where you’re coming from. After all, I’ve been reading George R. R. Martin for years.

  • Uncle Al

    The thing to do is to gently decelerate Ceres into Mars’ orbit, to dump its massive water content on Mars, for terraforming. The total 0.14 mass-% increment to Mars is minor. The water is welcome. The enthalpy of collision will volatize deposits into a Martian atmosphere. It’s our solar system. Let’s use it.

    8.96×10^20 kg Ceres
    6.39×10^23 kg Mars
    5.97×10^24 kg Earth

    • Mike Richardson

      Well, for once, I understand one of your posts, and it’s a pretty good point. I’m just wondering, though, if the amount of energy needed to move Ceres might be better put to use moving several smaller asteroids (or maybe some comets) and crashing them into the poles. Seems like Ceres is a lot of mass to get moving, even in space.

    • Randy McDonald

      The resulting impact on Mars would be catastrophic.

      Ceres has roughly a tenth of the mass of Mars, and is proportionally as massive as the Theia impactor thought to have produced the moon. The collision would resurface the planet. Far from making it more Earth-like, it would make it literally untouchable for a long period.

      The question of how to move Ceres is another thing.

      • Uncle Al

        Ceres is 100 times less mass than you state. A collision now will form a usefully hydrated planet by, oh, 2100 AD (the Enviro-whiner target for returning civilization to hunter-gatherer status). Wikipedia numbers,

        9.43×10^20 kg, 0.51 km/s escape velocity, Ceres
        6.4185×10^23 kg, 5.027 km/s Escape velocity, Mars

        Ceres/Mars = 0.00147 mass/mass
        Impact speed minimum 5.537 km/sec (3.44 miles/sec)

        I’m not saying Mars wouldn’t get its hair mussed. But I do say no more than a century or so to obtain an inhabitable planet post-collision. Ceres must inspiral, losing energy, Wrap it with a coil and let the solar wind de-orbit it. Low Earth to geostationary orbit is /_v = 4.66 km/s. Mars 24.13 km/s oribtial, Ceres 17.882 km/s orbital, /_v = 6.428 km/s.

        • Randy McDonald

          I stand corrected–it’s a bit more than 1% of the mass of the moon, and 0.14% of the mass of Mars. My memory was faulty.

          That said …

          “I’m not saying Mars wouldn’t get its hair mussed.”

          Mars would get resurfaced. How could this not happen if a massive body one-seventh of its diameter impacted it? Would this necessarily even result in a habitable world?

          And, again, how would Ceres be moved? What is a “coil”?

          • Uncle Al

            Melting then vaporizing 200 million km^3 of Ceres’ water cools the enthalpy of collision. Post with references was censored. I’m an AAAS member for 38 years. Nice.

          • Randy McDonald


    • Rope_Necktie

      Mars has virtually no magnetic field and therefore a very thin atmosphere. All else aside, the water would quickly evaporate and dissipate. To retain water, first you need a magnetic field and a viable atmosphere.

    • Jacob Lively

      Two routes can be taken-
      Step 1: Breed lichens to survive on Mars.
      Step 2: Disperse these across large swathes of the martian poles and regions around them.
      Step 3: Wait several hundred years, introducing new plant life as the oxygen content increases.
      Step 4: Go there yourself.

      Or… Just go for paraterraforming rather than terraforming. Domed cities ftw!

      I believe it quite likely that while we will never have large cities on Mars, it may serve as adequate farmland.

  • stevlich

    One thing that’s guaranteed is that NASA will never find life anywhere,
    just planetary and celestial features. Nobody cares about that crap
    anymore. Show me a Masai Mara on Ceres and then we’re talking. But
    NASA won’t even find an amoeba anywhere. Such incorrigible bastards.

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