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NASA astronauts Linda Godwin and Scott Altman have announced plans to leave the agency.

Spiral galaxy NGC 4921 presently is estimated to be 320 million light years distant. This image, taken by the Hubble Space Telescope, is being used to identify key stellar distance markers known as Cepheid variable stars. The magnificent spiral NGC 4921 has been informally dubbed anemic because of its low rate of star formation and low surface brightness. Visible in the image are, from the center, a bright nucleus, a bright central bar, a prominent ring of dark dust, blue clusters of recently formed stars, several smaller companion galaxies, unrelated galaxies in the far distant universe, and unrelated stars in our Milky Way Galaxy. Image Credit: NASA, ESA, K. Cook (LLNL)

NASA’s Commercial Reusable Suborbital Research Program (CRuSR) has awarded a total of approximately $475,000 to Armadillo Aerospace of Rockwall, Texas and Masten Space Systems of Mojave, Calif.

Is this one galaxy or two? Astronomer Art Hoag first asked this question when he chanced upon this unusual extragalactic object. On the outside is a ring dominated by bright blue stars, while near the center lies a ball of much redder stars that are likely much older. Between the two is a gap that appears almost completely dark. How Hoag’s Object formed remains unknown, although similar objects have been identified and collectively labeled as a form of ring galaxy. Genesis hypotheses include a galaxy collision billions of years ago and the gravitational effect of a central bar that has since vanished. This image, taken by the Hubble Space Telescope in July 2001, reveals unprecedented details of Hoag’s Object and may yield a better understanding. Hoag’s Object spans about 100,000 light years and lies about 600 million light years away toward the constellation of the Snake (Serpens). Coincidentally, visible in the gap (at about one o’clock) is yet another ring galaxy that likely lies far in the distance. Image Credit: NASA, R. Lucas (STScI/AURA)

From 5:30-6 p.m. EDT, NASA Television will air excerpts of an interview with Dr. Michael Duncan, who is leading a NASA team to Chile. NASA has been asked by the Chilean government through the U.S. Department of State to provide technical advice that might assist the trapped miners at the San Jose gold and copper mine near Copiapo, Chile.

The picturesque, but snow-capped volcanoes, composing the Islands of the Four Mountains in Alaska’s Aleutian Island chain look suspiciously like an alien world in this August 2010 image from the ASTER camera aboard NASA’s orbiting Terra satellite. The islands contain restless Mt. Cleveland, an active volcano currently being watched to see if it emits an ash cloud that could affect air travel over parts of North America. A close look at Mt. Cleveland, seen near the image center, shows red vegetation (false color), a white snow-covered peak, a light plume of gas and ash, and dark lanes where ash and debris fell or flowed. Millions of volcanoes have likely been active over the turbulent history of the Earth’s surface, while about 20 volcanoes are erupting even today, at any given time. Image Credit: NASA

NASA Awards Facility Operating Services Contract Award Term Period 1

Orcus Patera is an enigmatic elliptical depression near Mars’s equator, in the eastern hemisphere of the planet. Located between the volcanoes of Elysium Mons and Olympus Mons, its formation remains a mystery.

One of the most complex space scientific instruments ever built, the Alpha Magnetic Spectrometer (AMS-02) arrived at the Kennedy Space Center in Florida, escorted by astronauts who will fly with it on the Space Shuttle in February 2011.

Cloudless skies allowed a clear view of dust and hydrogen sulfide plumes along the coast of Namibia in early August 2010. The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA?s Terra satellite captured this natural-color image on Aug. 10, 2010. Multiple dust plumes blow off the coast toward the ocean, most or all of them probably arising from streambeds. Unlike the reddish-tan sands comprising the dunes directly south of the Kuiseb River, the stream-channel sediments are lighter in color. Wind frequently pushes dust plumes seaward along the Namibian Coast. Easterly trade winds blow from the Indian Ocean over the African continent, losing much of their moisture as they go. The winds are hot and dry as they pass over Namibia?s coastal plain, where they are prone to stir fine sediments. Even with dust plumes overhead, the marked change in land cover is obvious along the Kuiseb River. South of the river, sand dunes predominate, but the vegetation along the Kuiseb River prevents the dunes from advancing northward. North of the river, the land surface consists primarily of gravel plains punctuated by rocky hills. Hydrogen sulfide appears as a swath of irridescent green running parallel to the coast north of Walvis Bay. A 2009 study linked the emissions in this region to ocean currents, biological activity in the water column, and carbon-rich organic sediments under the water column. The meeting of hydrogen sulfide gas and oxygen-rich surface waters causes pure sulfur to precipitate into the water. The sulfur?s yellow color makes the water appear green to the satellite sensor. Image Credit: NASA