[meteorite-list] Dawn Mission Celebrates 10 Years in Space

[Ron Baalke]

https://www.jpl.nasa.gov/news/news.php?feature=6955

Dawn Mission Celebrates 10 Years in Space
Jet Propulsion Laboratory
September 27, 2017

Ten years ago, NASA's Dawn spacecraft set sail for the two most massive 
bodies in the asteroid belt between Mars and Jupiter: giant asteroid Vesta 
and dwarf planet Ceres. The mission was designed to deliver new knowledge 
about these small but intricate worlds, which hold clues to the formation 
of planets in our solar system.

"Our interplanetary spaceship has exceeded all expectations in the last 
decade, delivering amazing insights about these two fascinating bodies," 
said Chris Russell, principal investigator of the Dawn mission, based 
at the University of California, Los Angeles.

Since its launch on Sept. 27, 2007, Dawn has achieved numerous technical 
and scientific feats while traveling 4 billion miles (6 billion kilometers). 
It is the only spacecraft to orbit two extraterrestrial solar system targets. 
It is also the only spacecraft to orbit a dwarf planet, a milestone it 
achieved when in entered orbit around Ceres on March 6, 2015. The spacecraft's 
ion propulsion system enabled Dawn to study each of these worlds from 
a variety of vantage points and altitudes, creating an impressive scrapbook 
of 88,000 photos. Additionally, Dawn's suite of instruments enabled it 
to take a variety of other measurements of Vesta and Ceres, revealing 
the contrasting compositions and internal structures of these two bodies.

Vesta Highlights

Scientists learned a great deal about Vesta's geological features and 
composition during Dawn's 14 months of exploration there. A notable discovery 
was that Rheasilvia, a giant basin in Vesta's southern hemisphere, was 
even deeper and wider than scientists expected based on telescopic observations 
from Earth. It spans more than 310 miles (500 kilometers) and pierces 
about 12 miles (19 kilometers) into Vesta. The center of the crater also 
hosts a mountain twice the height of Mt. Everest -- the tallest feature 
seen in Dawn's 1,298 orbits of Vesta.

The massive punch into Vesta that carved out this crater happened about 
1 billion years ago and caused huge amounts of material to rain down on 
the surface. The net result is that the surface of the southern hemisphere 
of Vesta is younger than the northern hemisphere, which retains a hefty 
record of craters. The Rheasilvia impact also created dozens of gorges 
circling Vesta's equator. Canyons there, some of which formed from an 
earlier impact, measure up to 290 miles (465 kilometers) in length.

Ceres Highlights

One of Dawn's biggest revelations at Ceres is the extremely bright, salty 
material in Occator Crater that gleams amid an otherwise dark area. What 
appeared to be a single white blob at a distance turned out to be a smattering 
of many bright areas called faculae. The central bright area, Cerealia 
Facula, has a dome at its center with radial fractures across it that 
appears reddish in enhanced color images. This "bright spot" suggests 
Ceres was geologically active in the very recent past, when briny water 
rose to the surface and deposited salts. Just to the east are the Vinalia 
Faculae, a constellation of less-bright spots distributed along fractures 
that also intrigue scientists. Ceres hosts more than 300 small bright 
areas, with some thought to host ice at northern latitudes.

Another huge surprise at Ceres was Ahuna Mons, which scientists believe 
formed as a cryovolcano, a volcano that erupted with salty water in the 
past. This "lonely mountain," 3 miles (5 kilometers) high on its steepest 
side, is unlike anything else on Ceres and remains a thriving research 
topic. Though both Ahuna Mons and Occator appear dormant, they suggest 
that liquid water flowed once beneath the surface of Ceres, and may even 
still be there today, if it is enriched in salts that would lower its 
freezing point.

Dawn Science Continues

"The science team is still actively exploring the troves of data that 
Dawn has delivered so far, comparing these two fossils of the early solar 
system," said Carol Raymond, Dawn deputy principal investigator, based 
at NASA's Jet Propulsion Laboratory, Pasadena, California.

Since March 2015, Dawn has orbited Ceres 1,595 times. It remains healthy, 
currently in a 30-day elliptical orbit collecting data on cosmic rays 
in the vicinity of Ceres.

"This continues to be a mission for everyone who yearns for new knowledge, 
everyone who is curious about the cosmos, and everyone who is exhilarated 
by bold adventures into the unknown," said Marc Rayman, mission director 
and chief engineer, based at JPL.

Dawn's mission is managed by the Jet Propulsion Laboratory 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, the Max Planck Institute for Solar System Research, 
the Italian Space Agency and the Italian National Astrophysical Institute 
are international partners on the mission team. For a complete list of 
acknowledgments, see http://dawn.jpl.nasa.gov/mission.

For more information about the Dawn mission, visit:

https://dawn.jpl.nasa.gov

News Media Contact
Elizabeth Landau
Jet Propulsion Laboratory, Pasadena, Calif.
818-354-6425
elizabeth.landau at jpl.nasa.gov

2017-249