FROM: NASA
Thermal Tides at Mars
This diagram illustrates Mars' "thermal tides," a weather phenomenon responsible for large, daily variations in pressure at the Martian surface. Sunlight heats the surface and atmosphere on the day side of the planet, causing air to expand upwards. At higher levels in the atmosphere, this bulge of air then expands outward, to the sides, in order to equalize the pressure around it, as shown by the red arrows. Air flows out of the bulge, lowering the pressure of air felt at the surface below the bulge. The result is a deeper atmosphere, but one that is less dense and has a lower pressure at the surface, than that on the night side of the planet. As Mars rotates beneath the sun, this bulge moves across the planet each day, from east to west. A fixed observer, such as NASA's Curiosity rover, measures a decrease in pressure during the day, followed by an increase in pressure at night. The precise timing of the increase and decrease are affected by the time it takes the atmosphere to respond to the sunlight, as well as a number of other factors including the shape of the planet's surface and the amount of dust in the atmosphere.
Image credit: NASA/JPL-Caltech/Ashima Research/SWRI
FROM: NASA
Titan's Lake District, One Season Later
These images obtained by NASA's Cassini spacecraft show Titan's stable northern lake district. Cassini's radar instrument obtained the recent images on May 22, 2012. It observed some previously unseen regions but also some regions containing lakes that were last observed about six years-nearly one Titan season--ago. This marks the longest time interval between lake observations in the northern hemisphere.
The top image here shows part of the radar swath from May 22, 2012, centered near 79 degrees north latitude, 58 degrees west longitude, and about 220 by 47 miles (350 by 75 kilometers) in dimension. At the bottom, parts of this image are compared with those obtained in 2006. (The images appear slightly different from previous releases because they use a new filtering technique). In 2006, it was winter in the northern hemisphere and the lakes were in the dark. Although Titan spring began in 2009 and the sun has now risen over the lakes, there is no apparent change in lake levels since the 2006 flybys, consistent with climate models that predict stability of liquid lakes over several years. This shows that the northern lakes are not transient weather events, in contrast to the temporary darkening of parts of the equator after a rainstorm in 2010 (PIA 12819).
Changes in lake levels may still be detected later in the mission as Cassini continues to observe these high northern latitudes into the beginning of summer in 2017. At that point, the sun may cause evaporation. However, the lack of significant change over six years sets important constraints for climate models and the stability of liquids on Titan. Illumination is coming from the bottom.
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, DC. The Cassini orbiter was designed, developed and assembled at JPL. The radar instrument was built by JPL and the Italian Space Agency, working with team members from the United States and several European countries. Image Credit: NASA/JPL-Caltech/ASI
FROM: NASA
NASA, BIGELOW OFFICIALS TO DISCUSS SPACE STATION EXPANDABLE MODULE WASHINGTON
-- NASA has awarded a $17.8 million contract to Bigelow Aerospace to provide a new addition to the International Space Station. The Bigelow Expandable Activity Module will demonstrate the benefits of this space habitat technology for future exploration and commercial space endeavors. "The International Space Station is a unique laboratory that enables important discoveries that benefit humanity and vastly increase understanding of how humans can live and work in space for long periods," NASA Deputy Administrator Lori Garver said. "This partnership agreement for the use of expandable habitats represents a step forward in cutting-edge technology that can allow humans to thrive in space safely and affordably, and heralds important progress in U.S. commercial space innovation." Garver and Bigelow Aerospace Founder and President Robert Bigelow will discuss the Bigelow Expandable Activity Module program at a media availability at 1:30 p.m. EST (10:30 a.m. PST) Wednesday, Jan. 16, at Bigelow Aerospace facilities located at 1899 W. Brooks Ave. in North Las Vegas.
FROM: NASA
Opportunity at 'Copper Cliff,' Sol 3153, Stereo View
This 180-degree, stereo mosaic of images from the navigation camera on the NASA Mars Exploration Rover Opportunity shows terrain near the rover during the 3,153rd Martian day, or sol, of the rover's work on Mars (Dec. 6, 2012). West is at the center, south at the left edge, north at the right edge. The view appears in three dimensions when viewed through red-blue glasses with the red lens on the left.
Opportunity had driven about 7 feet (2.2 meters) westward earlier on Sol 3153 to get close to the outcrop called "Copper Cliff," which is in the center of this scene. The location is on the east-central portion of "Matijevic Hill" on the "Cape York" segment of the western rim of Endeavour Crater.
The view is presented as a cylindrical-perspective projection.
Credit-NASA-JPL-Caltech
Panoramic View From Near 'Point Lake' in Gale Crater, Sol 106
This panorama is a mosaic of images taken by the Mast Camera (Mastcam) on the NASA Mars rover Curiosity during the 106th Martian day, or sol, of the mission (Nov. 22, 2012). The rover was near a location called "Point Lake" for an overlook of a shallow depression called "Yellowknife Bay" which is in the left third of this scene, in the middle distance.
The image spans 360 degrees, with south at the center. It has been white-balanced to show what the rocks and soils in it would look like if they were on Earth.
Image Credit-NASA-JPL-Caltech-Malin Space Science Systems
FROM: U.S. DEPARTMENT OF DEFENSE
by jtozer
Saturday Space Sight: Ion Thruster Sets World Record
While the Dawn spacecraftis visiting the asteroids Vesta and Ceres, NASA Glenn has been developing the next generation of ion thrusters for future missions. NASA's Evolutionar Xeon Thruster (NEXT) Project has developed a 7-kilowatt ion thruster that can provide the capabilities needed in the future.
An ion thruster produces small levels of thrust relative to chemical thrusters, but does so at higher specific impulse (or higher exhaust velocities), which means that an ion thruster has a fuel efficiency of 10-12 times greater than a chemical thruster.
The higher the rocket’s specific impulse (fuel efficiency), the farther the spacecraft can go with a given amount of fuel.
Given that an ion thruster produces small levels of thrust relative to chemical thrusters, it needs to operate in excess of 10,000 hours to slowly accelerate the spacecraft to speeds necessary to reach the asteroid belt or beyond.
The NEXT ion thruster has been operated for over 43,000 hours, which for rocket scientists means that the thruster has processed over 770 kilograms of xenon propellant and can provide 30 million-newton-seconds of total impulse to the spacecraft. This demonstrated performance permits future science spacecraft to travel to varied destinations, such as extended tours of multi-asteroids, comets, and outer planets and their moons.
Photo Credit: NASA
FROM: NASA
Mountain Winds at Gale Crater
This graphic shows the pattern of winds predicted to be swirling around and inside Gale Crater, which is where NASA's Curiosity rover landed on Mars. Modeling the winds gives scientists a context for the data from Curiosity's Rover Environmental Monitoring Station (REMS).
Curiosity's current location is marked with an "X." The rover's setting within a broad depression between the mountain dubbed "Mount Sharp" to the southeast and the rim of Gale Crater to the northwest strongly affects wind measurements collected by REMS.
This snapshot shows midday conditions. In the daytime, winds rise out of the crater, shown by the red arrows, and up the mountain, shown by the yellow arrows. Blue arrows indicate winds that flow along the depression and seem, to Curiosity, to be coming up out of the depression since Curiosity is near the bottom. At its current location, Curiosity may be seeing a mixture of these winds, making it challenging to understand its weather readings.
The patterns reverse in the evening and overnight, when winds flow in the downhill direction.
The background image is an oblique view of Gale Crater, looking toward the southeast. It is an artist's impression using two-fold vertical exaggeration to emphasize the area's topography. The crater's diameter is 96 miles (154 kilometers).
The image combines elevation data from the High Resolution Stereo Camera on the European Space Agency's Mars Express orbiter, image data from the Context Camera on NASA's Mars Reconnaissance Orbiter, and color information from Viking Orbiter imagery.
Image credit: NASA/JPL-Caltech/ESA/DLR/FU Berlin/MSSS
