Posts tagged NASA
STRONGEST EVIDENCE YET INDICATES ICY SATURN MOON HIDING SALTWATER OCEAN
Jun 22nd
The new discovery was made during the Cassini-Huygens mission to Saturn, a collaboration of NASA, the European Space Agency and the Italian Space Agency. Launched in 1997, the mission spacecraft arrived at the Saturn system in 2004 and has been touring the giant ringed planet and its vast moon system ever since.
The plumes shooting water vapor and tiny grains of ice into space were originally discovered emanating from Enceladus — one of 19 known moons of Saturn — by the Cassini spacecraft in 2005. The plumes were originating from the so-called “tiger stripe” surface fractures at the moon’s south pole and apparently have created the material for the faint E Ring that traces the orbit of Enceladus around Saturn.
During three of Cassini’s passes through the plume in 2008 and 2009, the Cosmic Dust Analyser, or CDA, on board measured the composition of freshly ejected plume grains. The icy particles hit the detector’s target at speeds of up to 11 miles per second, instantly vaporizing them. The CDA separated the constituents of the resulting vapor clouds, allowing scientists to analyze them.
The study shows the ice grains found further out from Enceladus are relatively small and mostly ice-poor, closely matching the composition of the E Ring. Closer to the moon, however, the Cassini observations indicate that relatively large, salt-rich grains dominate.
“There currently is no plausible way to produce a steady outflow of salt-rich grains from solid ice across all the tiger stripes other than the salt water under Enceladus’ icy surface,” said Frank Postberg of the University of Germany, lead author of a study being published in Nature on June 23. Other co-authors include Jürgen Schmidt from the University of Potsdam, Jonathan Hillier from Open University headquartered in Milton Keynes, England, and Ralf Srama from the University of Stuttgart.
“The study indicates that ‘salt-poor’ particles are being ejected from the underground ocean through cracks in the moon at a much higher speed than the larger, salt-rich particles,” said CU-Boulder faculty member and study co-author Sascha Kempf of the Laboratory for Atmospheric and Space Physics.
“The E Ring is made up predominately of such salt-poor grains, although we discovered that 99 percent of the mass of the particles ejected by the plumes was made up of salt-rich grains, which was an unexpected finding,” said Kempf. “Since the salt-rich particles were ejected at a lower speed than the salt-poor particles, they fell back onto the moon’s icy surface rather than making it to the E Ring.”
According to the researchers, the salt-rich particles have an “ocean-like” composition that indicates most, if not all, of the expelled ice comes from the evaporation of liquid salt water rather than from the icy surface of the moon. When salt water freezes slowly the salt is “squeezed out,” leaving pure water ice behind. If the plumes were coming from the surface ice, there should be very little salt in them, which was not the case, according to the research team.
The researchers believe that perhaps 50 miles beneath the surface crust of Enceladus a layer of water exists between the rocky core and the icy mantle that is kept in a liquid state by gravitationally driven tidal forces created by Saturn and several neighboring moons, as well as by heat generated by radioactive decay.
According to the scientists, roughly 440 pounds of water vapor is lost every second from the plumes, along with smaller amounts of ice grains. Calculations show the liquid ocean must have a sizable evaporating surface or it would easily freeze over, halting the formation of the plumes. “This study implies that nearly all of the matter in the Enceladus plumes originates from a saltwater ocean that has a very large evaporating surface,” said Kempf.
Salt in the rock dissolves into the water, which accumulates in a liquid ocean beneath the icy crust, according to the Nature authors. When the outermost layer of the Enceladus crust cracks open, the reservoir is exposed to space. The drop in pressure causes the liquid to evaporate into a vapor, with some of it “flash-freezing” into salty ice grains, which subsequently creates the plumes, the science team believes.
“Enceladus is a tiny, icy moon located in a region of the outer Solar System where no liquid water was expected to exist because of its large distance from the sun,” said Nicolas Altobelli, ESA’s project scientist for the Cassini-Huygens mission. “This finding is therefore a crucial new piece of evidence showing that environmental conditions favorable to the emergence of life may be sustainable on icy bodies orbiting gas giant planets.”
The Huygens probe was released from the main spacecraft and parachuted through the atmosphere to the surface of Saturn’s largest moon, Titan, in 2005.
The Cassini spacecraft is carrying 12 science instruments, including a $12.5 million CU-Boulder ultraviolet imaging spectrograph designed and built by a LASP team led by Professor Larry Esposito.
CU ROLE IN DREAM CHASER SPACECRAFT TO CONTINUE UNDER NEW NASA GRANT TO SIERRA NEVADA CORP.
Apr 22nd
The Louisville, Colo.-based aerospace company was one of four companies to receive grants this week from NASA’s Commercial Crew Development program. The grant is a follow-on to Sierra Nevada’s NASA grant of $20 million for the Dream Chaser last year.
Roughly the size of a business jet, the 30-foot-long Dream Chaser is slated to launch vertically on an Atlas V rocket and land horizontally on conventional runways, similar to the much larger space shuttle. The spacecraft is based on NASA’s earlier HL-20 lifting body design.
As part of its continuing development of the Dream Chaser, Sierra Nevada will fund “human rating” research led by CU-Boulder Professor David Klaus of the aerospace engineering sciences department, according to Jim Voss, a CU faculty member and vice president of Sierra Nevada. Human rating research is aimed at developing a methodology for evaluating safety and operational aspects of spacecraft intended to transport crew.
“This is a great industry-academia collaboration that combines providing design input for the Dream Chaser to Sierra Nevada with four related thesis topics being pursued by Ph.D. students in our program,” Klaus said.
Sierra Nevada also will sponsor and fund a continuation of the CU-Boulder graduate student project involving Dream Chaser displays and controls, Voss said. The graduate project is focused on cockpit design and ergonomics evaluation to determine the best placement and type of controls to be used by the crew. The students are being advised by Voss and his colleague Joe Tanner, both of whom joined the CU-Boulder faculty after retiring as NASA astronauts.
Klaus, who heads the aerospace department’s bioastronautics focus area, has set up a laboratory in CU-Boulder’s Engineering Center housing three mock-ups of the spacecraft. One is a full-scale model of the Dream Chaser based on the earlier HL-20 design that is on loan from NASA to Sierra Nevada; another is a 15 percent scale model unit that was used for flight testing last December, and the third is the cockpit section being used to evaluate the layout for instrument displays and controls. A “public day” is being planned so that the community will have a chance to view the project.
“The University of Colorado and Sierra Nevada Corporation have formed a partnership that allows use of the tremendous intellectual resources of students and professors to help develop a commercial human spacecraft, the Dream Chaser,” said Voss. “I’m really pleased to continue the work that was started last year and look forward to more student involvement with this exciting project.”
-CU-