A closer look at enigmatic Ceres: NASA’s Dawn mission extended for second time

Artist’s conception of Dawn orbiting Ceres. Soon the spacecraft will be in its lowest-ever orbit around the dwarf planet. Image Credit: NASA/JPL-Caltech

NASA’s Dawn spacecraft has been orbiting the dwarf planet Ceres since March 2015, providing the first close-up views of this rocky and icy world residing in the main asteroid belt between Mars and Jupiter. Now, NASA announced that the mission will be extended, for the second time now. This is great news, partly because Dawn will be able to orbit closer to Ceres than it ever did before.

Dawn was the first spacecraft to orbit two different bodies in the Solar System, first the asteroid Vesta for 14 months from 2011 to 2012, and now Ceres since 2015. The voyage to both Vesta and Ceres was not an easy one, as reported recently, but it was absolutely worthwhile. There had been some discussion of possibly having Dawn go to a third target, the asteroid Adeona, but the first mission extension last year meant it would remain at Ceres until its fuel eventually runs out.

Closest view so far of the bright spots in Occator crater. Photo Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
Over 130 such bright spots have been found on Ceres. Photo Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
Ceres in natural color. Photo Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
False-colour image of Ceres, to highlight differences in surface materials. Image Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

In the new extension, Dawn will be placed in an elliptical orbit which can bring the spacecraft to within 200 kilometres (120 miles) of the surface. This would of course allow for even higher resolution images to be taken than before, especially of features such as the unusual bright spots, which scientists think are salt deposits, perhaps left over from evaporating water. The closest that Dawn had orbited Ceres previously was 385 kilometres (240 miles).

Another objective will be to use Dawn’s gamma ray and neutron spectrometer to study the surface and determine how much ice there is in Ceres’ uppermost surface layer. Dawn will also measure Ceres’ mineralogy with its visible and infrared mapping spectrometer.

During the mission extension, Ceres will also reach perihelion, when it is closest to the Sun, in April 2018. It is at this time when scientists hope to detect water vapour coming from Ceres’ surface.

View of Ahuna Mons, the “Lonely Mountain.” Photo Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA/PSI

Unlike the Cassini probe, which plunged, on purpose, into Saturn’s atmosphere at the end of its mission last month, Dawn will remain in orbit after its fuel runs out, sometime in the second half of 2018, in order to prevent contamination of the surface.

Scientists had previously observed that the bright spots appear to change in brightness from day to night, evidence of ongoing geological activity inside Ceres. The brightest and most well-known spots are in Occator crater, but over 130 have been found so far. Dawn has also seen haze above the bright spots and found organic material on the surface.

According to Chris Russell, principal investigator of the Dawn mission, as reported in Gizmodo: “We believe this is a huge salt deposit. We know it’s not ice and we’re pretty sure it’s salt, but we don’t know exactly what salt at the present time.”

Before Ceres, the Dawn spacecraft visited the asteroid Vesta. Photo Credit: NASA

“The global nature of Ceres’ bright spots suggests that this world has a subsurface layer that contains briny water-ice,” said Andreas Nathues at Max Planck Institute for Solar System Research in Göttingen, Germany. He noted, however, that “The whole picture we do not have yet.”

The “Lonely Mountain” (aka Ahuna Mons) is another odd feature on Ceres, an isolated, oval-shaped hill, 4,000 metres (13,000 feet) tall, which sits at the edge of a crater with nothing else similar anywhere nearby. It may be a product of subsurface crypvolcanism, according to scientists.

Dawn has already shown us two worlds never seen up close before, and there is now more to come. As previously and accurately noted by Sarah Gavit of NASA’s Jet Propulsion Laboratory (JPL) back in 2001, “Ceres and Vesta are two of the large unexplored worlds in our Solar System. We’ll learn about early planet formation in ways that wouldn’t have been possible before this mission.”

This article was first published on AmericaSpace.

 

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Egg-shaped dwarf planet Haumea has a ring, astronomers discover

Artist’s conception of the ring around dwarf planet Haumea. Image Credit: IAA-CSIC

Rings are fairly common in the Solar System – Saturn’s are the most famous, of course, but Jupiter, Uranus, and Neptune all have rings as well. They have also been discovered around two asteroid-like objects called centaurs, Chariklo and Chiron, between Jupiter and Neptune. Now, another ring system has been found, this time around the dwarf planet Haumea, which orbits the Sun way out past Pluto.

The ring was discovered by astronomers from the Institute of Astrophysics of Andalusia and the study has been published in the journal Nature. The astronomers found the ring by observing Haumea as it passed in front of a background star (an occultation).

“We predicted that Haumea would pass in front of a star on the 21st of January 2017, and twelve telescopes from ten different European observatories converged on the phenomenon,” said José Luis Ortiz, a researcher at the Institute of Astrophysics of Andalusia (IAA-CSIC). “This deployment of technical means allowed us to reconstruct with a very high precision the shape and size of dwarf planet Haumea, and discover to our surprise that it is considerably bigger and less reflecting than was previously believed. It is also much less dense than previously thought, which answered questions that had been pending about the object.”

Haumea is one of four dwarf planets known to exist beyond Neptune, including Pluto, Eris, and Makemake. It is elongated and egg-shaped rather than round, and its longest axis is 2,320 kilometres, almost the size of Pluto. While it takes 284 years to orbit the Sun, it spins rapidly on its axis, taking only 3.9 hours to complete one rotation.

The discovery was unexpected, and Haumea is now the most distant object in the Solar System known to have rings. When New Horizons flew past Pluto in 2015, it searched for any rings that might be there, but did not find any.

“One of the most interesting and unexpected findings was the discovery of a ring around Haumea,” said Pablo Santos-Sanz, another member of the IAA-CSIC team. “Until a few years ago we only knew of the existence of rings around the giant planets; then, recently, our team discovered that two small bodies situated between Jupiter and Neptune, belonging to a group called centaurs, have dense rings around them, which came as a big surprise. Now we have discovered that bodies even farther away than the centaurs, bigger and with very different general characteristics, can also have rings.”

The ring lies at a distance of 2,287 kilometres from the center of Haumea and is darker than the surface of the dwarf planet itself, making it difficult to detect. The ring is also on the equatorial plane of Haumea, as is the dwarf planet’s largest moon, Hi’iaka (there is also a second smaller moon, Namaka). Appearance-wise, the ring resembles those of Uranus and Neptune. Haumea and Hi’iaka are both thought to have water ice on their surfaces.

So how did the ring form?

“There are different possible explanations for the formation of the ring; it may have originated in a collision with another object, or in the dispersal of surface material due to the planet’s high rotational speed,” said Ortiz.

Two of the telescopes used, in Slovenia and Italy, had also received funding from The Planetary Society’s Gene Shoemaker Near Earth Object (NEO) Grant program. As noted by paper co-author Albino Carbognani:

“In the case of Haumea, it was thought there might be other satellites, in addition to the known ones, or a thin atmosphere (like Pluto’s). Instead, we found a ring. And this was the first ring discovered beyond Neptune!”

The observations also showed that Haumea probably lacks a global atmosphere like Pluto’s.

If Haumea has a ring, how many other small bodies in the outer Solar System might as well? Only further observations will help to answer that question; perhaps New Horizons will find some new ones as it continues its journey deeper into the Kuiper Belt beyond Pluto.

This article was first published on Futurism.

 

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Fly over Pluto and Charon for second anniversary of New Horizons’ historic visit

Pluto is a world of wonders, with vast glaciers and plains of nitrogen ice, mountains of water ice capped with methane snow, ancient rivers and lakes of liquid nitrogen, massive “ice spikes” reaching 500 metres tall (similar to Penitentes on Earth but much larger), a possible subsurface ocean and a hazy blue atmosphere. Photo Credit: NASA/JHUAPL/SwRI

It was two years ago today that NASA’s New Horizons spacecraft became the first-ever probe to visit Pluto in the cold, outer fringes of the Solar System. To help celebrate the occasion, NASA has posted a new video of the epic flyby, when the spacecraft soared over the tall mountains and vast icy plains of this small but active world.

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New moon discovered by Hubble orbiting third largest dwarf planet in Kuiper Belt

Two images of dwarf planet 2007 OR10 from Hubble, taken a year apart, showing the small moon. Image Credit: NASA/ESA/C. Kiss (Konkoly Observatory)/J. Stansberry (STScI)

Moons are exceedingly common in the Solar System – Jupiter alone has 67! But smaller planets do as well of course, except for Mercury and Venus, and even some dwarf planets and asteroids have moons. This includes dwarf planets such as Pluto, which has five moons despite being so small itself. Most of the larger dwarf planets are now known to possess moons, and now another one has been discovered, by the Hubble Space Telescope and two other telescopes, orbiting the third largest known dwarf planet known as 2007 OR10.

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‘Cracked and tipped over’ Pluto has a subsurface ocean: New evidence from New Horizons

View of Sputnik Planitia on Pluto. This vast region of nitrogen ice provides clues that a subsurface ocean of liquid water exists on Pluto. Photo Credit: NASA/JHUAPL/SwRI
View of Sputnik Planitia on Pluto. This vast region of nitrogen ice provides clues that a subsurface ocean of liquid water exists on Pluto. Photo Credit: NASA/JHUAPL/SwRI

Pluto, a tiny frigid world in the distant outskirts of the Solar System, has been full of surprises, as first revealed by the New Horizons spacecraft back in July 2015. Expected to be mostly a cold, geologically dead place, it has instead been shown to be quite the opposite. Yes, it’s bitterly cold of course, but New Horizons found ample evidence that it has also been geologically active in the past and in some ways still is. With tall mountains of solid water ice, ancient riverbeds carved by nitrogen rivers, vast plains, still-flowing glaciers of nitrogen ice, and possible ice volcanoes, Pluto is a wondrous world indeed. Another new finding makes it even more remarkable: evidence for a subsurface ocean of water. This had also been reported on previously by AmericaSpace, but the new update strengthens the case.

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