# The Dawn Mission Nearing the End

The 11-year Dawn mission is drawing to a close as the precious fuel runs out.

Well done all the same.

# The Interior of Ceres

One of the interesting things about Ceres is it is actually less dense (2161 Kg/cubic meter) than the Jupiter moon Europa (3013 Kg/cubic meter). It does begin to make more sense after learning there may be some sort of brine making up the interior.

Knowing the density we should be able to figure out how fast something falls.  Let’s try (hopefully I get the maths right):

We are clumsy and fall so our initial velocity is zero.  So the formula would be:

distance = 0.5*g*time^2 (that is time squared) and velocity = g*time.

We have a 30 meter platform.  if we fell off here on Earth gravity (9.8 m/sec2) we would hit the ground in about 1.4 seconds at a velocity of 14 m/sec – a very hard hit indeed.

On the Moon it would be (1.6 m/sec2) about 3.5 seconds to fall and we would hit at a velocity of 5.7 m/sec – a hard hit also, not as bad as on Earth but still hard.

And on Ceres (0.3 m/sec), the time to hit the ground would be by comparison a leisurely 8.2 seconds, ha we could take in the sights, our velocity would be  a tiny bit less than 2.5 m/s.  About like jogging straight into a wall and provided we did not puncture our space suit we would probably not suffer too much in the way of serious injury.

Anyway, sorry I couldn’t help myself, back to the image.

NASA’s caption: This artist’s concept summarizes our understanding of how the inside of Ceres could be structured, based on the data returned by the NASA’s Dawn mission.

Using information about Ceres’ gravity and topography, scientists found that Ceres is “differentiated,” which means that it has compositionally distinct layers at different depths. The most internal layer, the “mantle” is dominated by hydrated rocks, like clays. The external layer, the 24.85-mile (40-kilometer) thick crust, is a mixture of ice, salts, and hydrated minerals. Between the two is a layer that may contain a little bit of liquid rich in salts, called brine. It extends down at least 62 miles (100 kilometers). The Dawn observations cannot “see” below about 62 miles (100 kilometers) in depth. Hence, it is not possible to tell if Ceres’ deep interior contains more liquid or a core of dense material rich in metal.

Image: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

# The Bright Spots on Ceres

The Dawn mission released this mosaic image of one of the bright spots on the dwarf planet Ceres. The sodium carbonate (yes it’s washing soda) feature is basically a butte. How that would happen is puzzling.

NASA’s caption: This mosaic of a prominent mound located on the western side of Cerealia Facula was obtained by NASA’s Dawn spacecraft on June 22, 2018 from an altitude of about 21 miles (34 kilometers).

The geometry of this feature is similar to a mesa or large butte with a flat top. It has been puzzling scientists since its discovery in the early images of the Dawn mission at Ceres. These new images reveal many details. In particular, the relationships between the bright material, mostly composed of sodium carbonate, and the dark background might hold clues about the origin of the facula. This feature is located at about 19.5 degrees north latitude and 239.2 degrees east longitude.

Image: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

# Urvara and Yalode

Here’s a nice image of two large craters is from the Dawn spacecraft currently orbiting Ceres.

NASA — This image from NASA’s Dawn spacecraft shows the large craters Urvara (top) and Yalode (bottom) on dwarf planet Ceres. These features are so big that they must be observed from high altitudes in order to fit in the frame of a single image. Urvara is (101 miles (163 kilometers) in diameter, while Yalode is 162 miles (260 kilometers) in diameter.

The two giant craters were formed at different times. Yalode is almost 1 billion years older than Urvara, which is about 120 million to 140 million years old.

Yalode’s relatively smooth floor indicates Ceres’ crust material became close to — or even reached — the melting temperature of ice as a consequence of the heat generated by the impact. On the other hand, the smaller Urvara has rougher terrain. This suggests Urvara had either a lower temperature increase from the impact, or a colder crust temperature at the time of the crater’s formation, or a combination of the two. Indeed, Ceres’ interior was warmer in the past, and has been slowly cooling as its supply of radioactive isotopes, whose decay represents Ceres’ main heat source, has been decreasing over time.

This picture also reveals geological details such, as the feature Nar Sulcus inside Yalode and a central peak in Urvara.

Urvara is named after the Indian and Iranian deity of plants and fields. Yalode is named for the Dahomey goddess, worshipped by women at the harvest rites.

This image was obtained by NASA’s Dawn spacecraft on June 9, 2015. The spacecraft was then in its survey orbit (2,700 miles, 4,400 kilometers above the surface), when the footprint of Dawn’s framing camera on Ceres’ surface was about 260 miles (420 kilometers) across on Ceres’ surface. The resolution is 1,400 feet (410 meters) per pixel. The central coordinates of the picture are 43 degrees south latitude, 278 degrees east in longitude.

# Occator Crater

Well I am having such a difficult time trying to get these live feeds up this week. I am having troubles all around, for example we got an extra 25 cm of snow overnight added to the 15 we got yesterday. I’ll post a picture tomorrow.

So I love this image from data delivered by the Dawn spacecraft around Ceres, it is of course Occator crater and those bright spots.

Here’s the original caption to explain things:
This simulated perspective view shows Occator Crater, measuring 57 miles (92 kilometers) across and 2.5 miles (4 kilometers) deep, which contains the brightest area on Ceres. This region has been the subject of intense interest since Dawn’s approach to the dwarf planet in early 2015. This view, which faces north, was made using images from Dawn’s low-altitude mapping orbit, 240 miles (385 kilometers) above Ceres.

Dawn’s close-up view reveals a dome in a smooth-walled pit in the bright center of the crater. Numerous linear features and fractures crisscross the top and flanks of this dome. Prominent fractures also surround the dome and run through smaller, bright regions found within the crater. The central dome area is called Cerealia Facula and the dimmer bright areas are called Vinalia Faculae.

Image: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

# Dawn Mission Extended

The Dawn mission extended for about another year. Here’s the details:

NASA — NASA has authorized a second extension of the Dawn mission at Ceres, the largest object in the asteroid belt between Mars and Jupiter. During this extension, the spacecraft will descend to lower altitudes than ever before at the dwarf planet, which it has been orbiting since March 2015. The spacecraft will continue at Ceres for the remainder of its science investigation and will remain in a stable orbit indefinitely after its hydrazine fuel runs out.

The Dawn flight team is studying ways to maneuver Dawn into a new elliptical orbit, which may take the spacecraft to less than 120 miles (200 kilometers) from the surface of Ceres at closest approach. Previously, Dawn’s lowest altitude was 240 miles (385 kilometers).

A priority of the second Ceres mission extension is collecting data with Dawn’s gamma ray and neutron spectrometer, which measures the number and energy of gamma rays and neutrons. This information is important for understanding the composition of Ceres’ uppermost layer and how much ice it contains.

The spacecraft also will take visible-light images of Ceres’ surface geology with its camera, as well as measurements of Ceres’ mineralogy with its visible and infrared mapping spectrometer.

The extended mission at Ceres additionally allows Dawn to be in orbit while the dwarf planet goes through perihelion, its closest approach to the Sun, which will occur in April 2018. At closer proximity to the Sun, more ice on Ceres’ surface may turn to water vapor, which may in turn contribute to the weak transient atmosphere detected by the European Space Agency’s Herschel Space Observatory before Dawn’s arrival. Building on Dawn’s findings, the team has hypothesized that water vapor may be produced in part from energetic particles from the Sun interacting with ice in Ceres’ shallow surface. Scientists will combine data from ground-based observatories with Dawn’s observations to further study these phenomena as Ceres approaches perihelion.

The Dawn team is currently refining its plans for this next and final chapter of the mission. Because of its commitment to protect Ceres from Earthly contamination, Dawn will not land or crash into Ceres. Instead, it will carry out as much science as it can in its final planned orbit, where it will stay even after it can no longer communicate with Earth. Mission planners estimate the spacecraft can continue operating until the second half of 2018.

Dawn is the only mission ever to orbit two extraterrestrial targets. It orbited giant asteroid Vesta for 14 months from 2011 to 2012, then continued on to Ceres, where it has been in orbit since March 2015.

The Dawn mission is managed by JPL for NASA’s Science Mission Directorate in Washington. Dawn is a project of the directorate’s Discovery Program, managed by NASA’s Marshall Space Flight Center in Huntsville, Alabama. UCLA is responsible for overall Dawn mission science. Orbital ATK Inc., in Dulles, Virginia, designed and built the spacecraft. The German Aerospace Center, Max Planck Institute for Solar System Research, Italian Space Agency and Italian National Astrophysical Institute are international partners on the mission team.

Thanks and Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

# Juling Crater on Ceres

The Dawn mission is still going strong.  In fact Dawn just came to within 5,200 km / 3,230 mi of the surface of the dwarf planet Ceres (22 Aug 17).  The image below is from about two years ago on 25 Aug 2016 when Dawn was much closer, at an altitude of only 385 km / 240 mi.

This high-resolution image of Juling Crater on Ceres reveals, in exquisite detail, features on the rims and crater floor. The crater is about 1.6 miles (2.5 kilometers) deep and the small mountain, seen left of the center of the crater, is about 0.6 miles (1 kilometers) high. The many features indicative of the flow of material suggest the subsurface is rich in ice. The geological structure of this region, as seen in PIA21753, also generally suggests that ice is involved.

The origin of the small depression seen at the top of the mountain is not fully understood but might have formed as a consequence of a landslide, visible on the northeastern flank.

Juling is named after the Sakai/Orang Asli spirit of the crops from Malaysia.

NASA’s Dawn spacecraft acquired this picture on August 24, 2016. The image was taken during Dawn’s extended mission, from its low altitude mapping orbit at about 240 miles (385 kilometers) above the surface. The center coordinates of this image are 38 degrees south latitude, 165 degrees east longitude.

# Fly Overs

There are two, first New Horizons over Pluto:

And second, a flyover of Charon:

NASA (via YouTube) – Using actual New Horizons data and digital elevation models of Pluto and its largest moon Charon, mission scientists have created flyover movies that offer spectacular new perspectives of the many unusual features that were discovered and which have reshaped our views of the Pluto system – from a vantage point even closer than the spacecraft itself.

# Ceres at Opposition

Ceres diameter:  945 km / 587 miles.  Ceres is estimated to contain almost a third of mass of the entire asteroid belt.  Those movies with the spaceship having to do thrilling flying to get through the asteroid belt are far from being accurate.

NASA – This enhanced color image of Ceres’ surface was made from data obtained on April 29, 2017, when NASA’s Dawn spacecraft was exactly between the sun and Ceres. Dawn’s framing cameras took images of Ceres with a clear filter as well as five different color filters.

Images combining these different color filter perspectives reveal fine details of Ceres’ surface. For example, they emphasize the distinct compositions and textures of the material ejected from craters. The brightest region on Ceres, called Cerealia Facula, is highlighted in Occator Crater in the center of this image. Vinalia Faculae, the set of secondary bright spots in the same crater, are located to the right of Cerealia Facula.

One of the darkest regions on Ceres is next to Occator, and represents ejected material from the impact that formed the crater. The ejected material forms a large arc that extends over several hundred kilometers, below the center of Ceres in this image. That material’s distribution is partly determined by Ceres’ rotation.

Other craters also show a mixture of bright and dark regions. While the bright areas are generally identified as salt-rich material excavated from Ceres’ crust, the origin of the dark material remains to be explained. It may have been excavated from a different layer within Ceres’ subsurface than the rest of the ejecta blanket. Scientists will continue analyzing the color data to look for clues about the nature of the different materials on Ceres.

The blueish color is generally found in association with young craters. Scientists believe the color relates to processes that occur when an impact ejects and redistributes material on the surface. The continuous bombardment of Ceres’ surface by micrometeorites alters the texture of the exposed material, leading to its reddening.

Image Credit:  NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

# NavCam View of Ceres

A very nice look at Ceres from Dawn’s NAVCAM. The bright spot in Occator Crater at the top of the image.

The Dawn spacecraft is moving to a new orbit 20,000 km / 12,400 miles above Ceres, this image was taken on 28 March 2017 at a distance of 48,300 km / 30,000 miles. Dawn should be in place by the end of the month.

From NASA:
Several familiar features can be identified: At the top, we see Occator Crater and its faculae (bright deposits identified as a mixture of sodium carbonate and other salts). Below center is the crater Urvara, and to the right of it, the larger crater Yalode (the third and second largest craters on Ceres, respectively). Large-scale faults called Samhain Catenae stretch from the Occator region toward the Yalode-Urvara region.

This map can be used to locate these and more features. (Link goes off-site, use your back button to return)

Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA