miércoles, 22 de marzo de 2017

ROSETTA | The Many Faces of Rosetta’s Comet 67P | NASA

The Many Faces of Rosetta’s Comet 67P | NASA

The Many Faces of 

Rosetta’s Comet 67P

A 100 foot-wide (30 meter), 28-million-pound (12.8-million-kilogram) boulder
A 100 foot-wide (30 meter), 28-million-pound (12.8-million-kilogram) boulder, was found to have moved 460 feet (140 meters) on comet 67P/Churyumov–Gerasimenko in the lead up to perihelion in August 2015, when the comet’s activity was at its highest. In both images, an arrow points to the boulder; in the right-hand image, the dotted circle outlines the original location of the boulder for reference.
Several sites of cliff collapse on comet 67P/Churyumov–Gerasimenko
Several sites of cliff collapse on comet 67P/Churyumov–Gerasimenko were identified during Rosetta’s mission. The yellow arrows mark the fractures where the detachment occurred. The collapsed sections are about 50 feet (15 meters) long for the left-hand section, and 30 feet (9 meters) for the right-hand section. Additional images taken from greater distances suggest the collapse occurred between May and December 2015.
Comet 67P/Churyumov–Gerasimenko
This image showcases changes identified in high-resolution images of Comet 67P/Churyumov–Gerasimenko during more than two years of monitoring by ESA’s Rosetta spacecraft.
Credits: Top center images: ESA/Rosetta/NAVCAM, CC BY-SA 3.0 IGO; all others: ESA/Rosetta/MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA
Images returned from the European Space Agency’s Rosetta mission indicate that during its most recent trip through the inner solar system, the surface of comet 67P/Churyumov-Gerasimenko was a very active place – full of growing fractures, collapsing cliffs and massive rolling boulders. Moving material buried some features on the comet’s surface while exhuming others. A study on 67P’s changing surface was released Tuesday, March 21, in the journal Science.
“As comets approach the sun, they go into overdrive and exhibit spectacular changes on their surface,” said Ramy El-Maarry, study leader and a member of the U.S. Rosetta science team from the University of Colorado, Boulder. “This is something we were not able to really appreciate before the Rosetta mission, which gave us the chance to look at a comet in ultra-high resolution for more than two years.”
Most comets orbit our sun in highly elliptical orbits that cause them to spend most of their time in the extremely cold outer solar system. When a comet approaches the inner solar system, the sun begins to warm the ice on and near the comet’s surface. When the ice warms enough it can rapidly sublimate (turn directly from the solid to the vapor state). This sublimation process can occur with variable degrees of intensity and time-scales and cause the surface to change rapidly. Between August 2014 and September 2016, Rosetta orbited comet 67P during the comet’s swing through the inner-solar system.
“We saw a massive cliff collapse and a large crack in the neck of the comet get bigger and bigger,” said El-Maarry. “And we discovered that boulders the size of a large truck could be moved across the comet’s surface a distance as long as one-and-a-half football fields.”
In the case of the boulder, Rosetta’s cameras observed a 282-million-pound (130-million-kilogram), 100-feet-wide (30-meter) space rock to have moved 150 yards (460 feet, or 140 meters) from its original position on the comet’s nucleus. The massive space rock probably moved as a result of several outburst events that were detected close to its original position.
The warming of 67P also caused the comet’s rotation rate to speed up. The comet’s increasing spin rate in the lead-up to perihelion is thought to be responsible for a 1,600-foot-long (500-meters) fracture spotted in August 2014 that runs through the comet’s neck. The fracture, which originally extended a bit longer than the Empire State Building is high, was found to have increased in width by about 100 feet (30 meters) by December 2014. Furthermore, in images taken in June 2016, a new 500- to 1,000-foot-long (150 to 300 meters)  fracture was identified parallel to the original fracture.
“The large crack was in the ‘neck’ of the comet -- a small central part that connects the two lobes,” said El-Maarry. “The crack was extending--indicating that the comet may split up one day.”
Understanding how comets change and evolve with time gives us important insights into the types and abundance of ices in comets, and how long comets can stay in the inner solar system before losing all their ice and becoming balls of dust,” said El-Maarry. “This helps us better understand the conditions of the early solar system, and possibly even how life started.”
A link to an ESA press release with more information on the El-Maarry paper in Science can be found here:
In a second Rosetta study released Tuesday, this one published in Nature Astronomy, scientists make the first definitive link between an outburst of dust and gas from the nucleus of 67P and the collapse of one of its prominent cliffs, which also exposed the comet’s pristine, icy interior. 
A link to an ESA press release on the Nature Astronomy paper can be found here:
Comets are time capsules containing primitive material left over from the epoch when the sun and its planets formed. Rosetta was the first spacecraft to witness at close proximity how a comet changes as it is subjected to the increasing intensity of the sun's radiation. Observations will help scientists learn more about the origin and evolution of our solar system and whether comets brought life-sustaining water and organic molecules to the Earth.
Rosetta is an ESA mission with contributions from its member states and NASA. Rosetta's Philae lander is provided by a consortium led by the German Aerospace Center, Cologne; Max Planck Institute for Solar System Research, Gottingen; French National Space Agency, Paris; and the Italian Space Agency, Rome. JPL, Pasadena, California, a division of Caltech in Pasadena, manages the U.S. contribution of the Rosetta mission for NASA's Science Mission Directorate in Washington. JPL also built the MIRO instrument and hosts its principal investigator, Mark Hofstadter. The Southwest Research Institute (San Antonio and Boulder, Colorado), developed the Rosetta orbiter's IES and Alice instruments and hosts their principal investigators, James Burch (IES) and Joel Parker (Alice).
For more information on the U.S. instruments aboard Rosetta, visit:
More information about Rosetta is available at:
DC Agle
Jet Propulsion Laboratory, Pasadena, California

Dwayne Brown / Laurie Cantillo
NASA Headquarters, Washington
202-358-1726 / 202-358-1077
dwayne.c.brown@nasa.gov / laura.l.cantillo@nasa.gov 

Markus Bauer
European Space Agency, Noordwijk, Netherlands
Last Updated: March 21, 2017
Editor: Tony Greicius

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