Two of the Milky Way's Spiral Arms Go Missing

MEDIA RELATIONS OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109 TELEPHONE 818-354-5011

http://www.jpl.nasa.gov

Whitney Clavin 818-354-4673/818-648-9734
Jet Propulsion Laboratory, Pasadena, Calif.
whitney.clavin@jpl.nasa.gov

NEWS RELEASE: 2008-094 June 3, 2008

Two of the Milky Way's Spiral Arms Go Missing

St. Louis, Mo. -- For decades, astronomers have been blind to what our galaxy, the Milky
Way, really looks like. After all, we sit in the midst of it and can't step outside for a bird's
eye view.

Now, new images from NASA's Spitzer Space Telescope are shedding light on the true
structure of the Milky Way, revealing that it has just two major arms of stars instead of
the four it was previously thought to possess.

"Spitzer has provided us with a starting point for rethinking the structure of the Milky
Way," said Robert Benjamin of the University of Wisconsin, Whitewater, who presented
the new results at a press conference today at the 212th meeting of the American
Astronomical Society in St. Louis, Mo. "We will keep revising our picture in the same
way that early explorers sailing around the globe had to keep revising their maps."

An artist's concept of the structure of our two-armed Milky Way is online at

http://www.nasa.gov/mission_pages/spitzer/multimedia/20080603a.html .

Since the 1950s, astronomers have produced maps of the Milky Way. The early models
were based on radio observations of gas in the galaxy, and suggested a spiral structure
with four major star-forming arms, called Norma, Scutum-Centaurus, Sagittarius and
Perseus. In addition to arms, there are bands of gas and dust in the central part of the
galaxy. Our sun lies near a small, partial arm called the Orion Arm, or Orion Spur,
located between the Sagittarius and Perseus arms.

"For years, people created maps of the whole galaxy based on studying just one section
of it, or using only one method," said Benjamin. "Unfortunately, when the models from
various groups were compared, they didn't always agree. It's a bit like studying an
elephant blind-folded."

Large infrared sky surveys in the 1990s led to some major revisions of these models,
including the discovery of a large bar of stars in the middle of the Milky Way. Infrared
light can penetrate through dust, so telescopes designed to pick up infrared light get better
views of our dusty and crowded galactic center. In 2005, Benjamin and his colleagues
used Spitzer's infrared detectors to obtain detailed information about our galaxy's bar, and
found that it extends farther out from the center of the galaxy than previously thought.

The team of scientists now has new infrared imagery from Spitzer of an expansive swath
of the Milky Way, stretching 130 degrees across the sky and one degree above and below
the galaxy's mid-plane. This extensive mosaic combines 800,000 snapshots and includes
over 110 million stars.

Benjamin developed software that counts the stars, measuring stellar densities. When he
and his teammates counted stars in the direction of the Scutum-Centaurus Arm, they
noticed an increase in their numbers, as would be expected for a spiral arm. But, when
they looked in the direction where they expected to see the Sagittarius and Norma arms,
there was no jump in the number of stars. The fourth arm, Perseus, wraps around the
outer portion of our galaxy and cannot be seen in the new Spitzer images.

The findings make the case that the Milky Way has two major spiral arms, a common
structure for galaxies with bars. These major arms, the Scutum-Centaurus and Perseus
arms, have the greatest densities of both young, bright stars, and older, so-called red-giant
stars. The two minor arms, Sagittarius and Norma, are filled with gas and pockets of
young stars. Benjamin said the two major arms seem to connect up nicely with the near
and far ends of the galaxy's central bar.

"Now, we can fit the arms together with the bar, like pieces of a puzzle," said Benjamin,
"and, we can map the structure, position and width of these arms for the first time."
Previous infrared observations found hints of a two-armed Milky Way, but those results
were unclear because the position and width of the arms were unknown.

Though galaxy arms appear to be intact features, stars are actually constantly moving in
and out of them as they orbit the center of the Milky Way, like London commuters in a
busy traffic circle. Our own sun might have once resided in a different arm. Since it was
formed more than 4 billion years ago, it has traveled around the galaxy 16 times.

Co-investigators of this research include Ed Churchwell, Marilyn Meade and Brian
Babler of the University of Wisconsin, Madison; Barbara Whitney of the Space Science
Institute, Madison, Wis.; Rémy Indebetouw of the University of Virginia, Charlottesville;
and Christer Watson of Manchester College, Ind. NASA's Jet Propulsion Laboratory,
Pasadena, Calif., manages the Spitzer mission for NASA's Science Mission Directorate,
Washington. Science operations occur at the Spitzer Science Center at the California
Institute of Technology, also in Pasadena. For more information about Spitzer, visit

http://www.spitzer.caltech.edu/spitzer and http://www.nasa.gov/spitzer .

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Mars Odyssey THEMIS Images: May 19-23, 2008

MARS ODYSSEY THEMIS IMAGES
May 26-30, 2008

o Labeatis Catenae (Released 26 May 2008)

http://themis.asu.edu/zoom-20080526a

o Tartarus Montes (Released 27 May 2008)

http://themis.asu.edu/zoom-20080527a

o Kasei Channels (Released 28 May 2008)

http://themis.asu.edu/zoom-20080528a

o Kasei Valles (Released 29 May 2008)

http://themis.asu.edu/zoom-20080529a

o Kasei Valles (Released 30 May 2008)

http://themis.asu.edu/zoom-20080530a

All of the THEMIS images are archived here:

http://themis.asu.edu/latest.html

NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission
for NASA's Office of Space Science, Washington, D.C. The Thermal Emission
Imaging System (THEMIS) was developed by Arizona State University,
Tempe, in co.oration with Raytheon Santa Barbara Remote Sensing.
The THEMIS investigation is led by Dr. Philip Christensen at Arizona State
University. Lockheed Martin Astronautics, Denver, is the prime contractor
for the Odyssey project, and developed and built the orbiter. Mission
operations are conducted jointly from Lockheed Martin and from JPL, a
division of the California Institute of Technology in Pasadena.

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MRO HiRISE Images - May 28, 2008

MARS RECONNAISSANCE ORBITER HIRISE IMAGES
May 28, 2008

o Descent of the Phoenix Lander

http://hirise.lpl.arizona.edu/phoenix-descent.php

o First Image of Phoenix Lander Hardware: EDL + 11

http://hirise.lpl.arizona.edu/phoenix-hardware_11.php

o HiRISE Images Phoenix Lander Hardware: EDL + 22

http://hirise.lpl.arizona.edu/phoenix-hardware.php

o Gullies of Crater Wall in Terra Sirenum

http://hirise.lpl.arizona.edu/PSP_006760_1370

All of the HiRISE images are archived here:

http://hirise.lpl.arizona.edu/

Information about the Mars Reconnaissance Orbiter is online at

http://www.nasa.gov/mro. The mission is managed by NASA's Jet Propulsion
Laboratory, a division of the California Institute of Technology, for the NASA
Science Mission Directorate, Washington, D.C. Lockheed Martin Space Systems,
of Denver, is the prime contractor and built the spacecraft. HiRISE is operated by t
he University of Arizona. Ball Aerospace and Technologies Corp., of Boulder, Colo.,
built the HiRISE instrument.

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NASA'S Phoenix Lander Robotic Arm Camera Sees Possible Ice

MEDIA RELATIONS OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109 TELEPHONE 818-354-5011
http://www.jpl.nasa.gov

Guy Webster 818-354-5011
Jet Propulsion Laboratory, Pasadena, Calif.
Guy.webster@jpl.nasa.gov

Dwayne Brown 202-358-1726
NASA Headquarters, Washington
Dwayne.c.brown@nasa.gov

Sara Hammond 520-626-1974
University of Arizona, Tucson
shammond@lpl.arizona.edu

NEWS RELEASE: 2008-090 May 30, 2008

NASA'S Phoenix Lander Robotic Arm Camera Sees Possible Ice

TUCSON, Ariz.-- Scientists have discovered what may be ice that was exposed when soil was blown
away as NASA's Phoenix spacecraft landed on Mars last Sunday, May 25. The possible ice appears
in an image the robotic arm camera took underneath the lander, near a footpad.

"We could very well be seeing rock, or we could be seeing exposed ice in the retrorocket blast zone,"
said Ray Arvidson of Washington University, St. Louis, Mo., co-investigator for the robotic arm.
"We'll test the two ideas by getting more data, including color data, from the robotic arm camera. We
think that if the hard features are ice, they will become brighter because atmospheric water vapor will
collect as new frost on the ice.

"Full confirmation of what we're seeing will come when we excavate and analyze layers in the nearby
workspace," Arvidson said.

Testing last night of a Phoenix instrument that bakes and sniffs samples to identify ingredients
identified a possible short circuit. This prompted commands for diagnostic steps to be developed and
sent to the lander in the next few days. The instrument is the Thermal and Evolved Gas Analyzer. It
includes a calorimeter that tracks how much heat is needed to melt or vaporize substances in a
sample, plus a mass spectrometer to examine vapors driven off by the heat. The Thursday, May 29,
tests recorded electrical behavior consistent with an intermittent short circuit in the spectrometer
portion.

"We have developed a strategy to gain a better understanding of this behavior, and we have identified
workarounds for some of the possibilities," said William Boynton of the University of Arizona,
Tucson, lead scientist for the instrument.

The latest data from the Canadian Space Agency's weather station shows another sunny day at the
Phoenix landing site with temperatures holding at minus 30 degrees Celsius (minus 22 degrees
Fahrenheit) as the sol's high, and a low of minus 80 degrees Celsius (minus 112 degrees Fahrenheit).
The lidar instrument was activated for a 15-minute period just before noon local Mars time, and
showed increasing dust in the atmosphere.

"This is the first time lidar technology has been used on the surface of another planet," said the
meteorological station's chief engineer, Mike Daly, from MDA in Brampton, Canada. "The team is
elated that we are getting such interesting data about the dust dynamics in the atmosphere."

The mission passed a "safe to proceed" review on Thursday evening, meeting criteria to proceed with
evaluating and using the science instruments.

"We have evaluated the performance of the spacecraft on the surface and found we're ready to move
forward. While we are still investigating instrument performance such as the anomaly on TEGA
[Thermal and Evolved Gas Analyzer], the spacecraft's infrastructure has passed its tests and gets a
clean bill of health," said David Spencer of NASA's Jet Propulsion Laboratory, Pasadena, Calif.,
deputy project manager for Phoenix.

"We're still in the process of checking out our instruments," Phoenix project scientist Leslie Tamppari
of JPL said. "The process is designed to be very flexible, to respond to discoveries and issues that
come up every day. We're in the process of taking images and getting color information that will help
us understand soil properties. This will help us understand where best to first touch the soil and then
where and how best to dig."

The Phoenix mission is led by Peter Smith at the University of Arizona with project management at
JPL and development partnership at Lockheed Martin, Denver. International contributions come from
the Canadian Space Agency; the University of Neuchatel, Switzerland; the universities of
Copenhagen and Aarhus, Denmark; Max Planck Institute, Germany; and the Finnish Meteorological
Institute. For more about Phoenix, visit:

http://www.nasa.gov/phoenix

and
http://phoenix.lpl.arizona.edu.

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NASA Phoenix Mars Lander Puts Arm and Other Tools to Work

Contacts: Guy Webster 818-354-5011
Jet Propulsion Laboratory, Pasadena, Calif.
guy.webster@jpl.nasa.gov

Dwayne Brown 202-358-1726
NASA Headquarters, Washington
dwayne.c.brown@nasa.gov

Sara Hammond 520-626-1974
University of Arizona, Tucson
shammond@lpl.arizona.edu

News Release: 2008-089 May 29, 2008

NASA Phoenix Mars Lander Puts Arm and Other Tools to Work

TUCSON, Ariz. - NASA's Mars lander is returning more detailed images from the Martian surface
and is now preparing its instruments for science operations.

Phoenix transmitted a 360-degree panorama of its frigid Martian world, freed its nearly 8-foot robotic
arm, tested a laser instrument for studying dust and clouds, and transmitted its second weather report
on Wednesday evening.

"We've imaged the entire landing site, all 360 degrees of it. We see it all," said Phoenix principal
investigator Peter Smith, University of Arizona, Tucson. "You can see the lander in a fish-eye view
that goes all the way out to the entire horizon "We are now making plans for where to dig first, and
what we'll save for later."

Commands were communicated to Phoenix to rotate the robotic arm's wrist to unlatch its launch lock,
raise the forearm and move it upright to release the elbow restraint.

"We're pleased that we successfully unstowed the robotic arm. In fact, this is the first time we have
moved the arm in about a year," said Matthew Robinson of NASA's Jet Propulsion Laboratory in
Pasadena, Calif. The arm deployment brings the Phoenix mission to a significant milestone.

"We have achieved all of our engineering characterization prerequisites, with all the critical
deployments behind us," said JPL's Barry Goldstein, Phoenix project manager. "We're now at a phase
of the mission where we're characterizing the science payload instruments. That's a very important
step for us."

After a health check that tests the arm at a range of warmer and colder temperatures, the titanium and
aluminum arm will soon be tasked with its first assignment: to use its camera to look under the
spacecraft to assess the terrain and underside of the lander.

The robotic arm will later trench into the icy layers of northern polar Mars and deliver samples to
instruments that will analyze what this part of Mars is made of, what its water is like, and whether it
is or has ever been a possible habitat for life.

Another milestone for the mission included the activation of the laser instrument called light
detection and ranging instrument, or lidar.

"The Canadians are walking on moonbeams. It's a huge achievement for us," said Jim Whiteway
Canadian Science lead from York University, Toronto. The lidar is a critical component of Phoenix's
weather station, provided by the Canadian Space Agency. The instrument is designed to detect dust,
clouds and fog by emitting rapid pulses of green laser-like light into the atmosphere. The light
bounces off particles and is reflected back to a telescope.

"One of the main challenges we faced was to deliver the lidar from the test lab in Ottawa, Canada, to
Mars while maintaining its alignment within one one-hundredth of a degree," said Whiteway. "That's
like aiming a laser pointer at a baseball at a distance from home plate to the center field wall, holding
that aim steady after launch for a year in space, then landing," he added.

Lidar data shows dust aloft to a height of 3.5 kilometers (2 miles). The weather at the Phoenix
landing site on the second day following landing was sunny with moderate dust, with a high of minus
30 degrees Celsius (minus 22 degrees Fahrenheit) and a low of minus 80 (minus 112 degrees
Fahrenheit).

The Phoenix mission is led by Smith at the University of Arizona with project management at JPL
and development partnership at Lockheed Martin, Denver. International contributions come from the
Canadian Space Agency; the University of Neuchatel, Switzerland; the universities of Copenhagen
and Aarhus, Denmark; Max Planck Institute, Germany; and the Finnish Meteorological Institute. For
more about Phoenix, visit:

http://www.nasa.gov/phoenix .

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Scientists Hold Seance for Supernova

Media contact: Whitney Clavin 818-354-4673
Jet Propulsion Laboratory, Pasadena, Calif.
whitney.clavin@jpl.nasa.gov

News Release: 2008-088 May 29, 2008

Scientists Hold Seance for Supernova

Astronomers have unearthed secrets from the grave of a star that blasted apart in a
supernova explosion long ago. By decoding ghostly echoes of light traveling away from
the remains of a supernova called Cassiopeia A, the scientists have pieced together what
the star looked like in life, and ultimately how it met its demise.

The discovery, made using primarily NASA's Spitzer Space Telescope and Japan's
Subaru telescope on Mauna Kea in Hawaii, represents the first time astronomers have
been able to resurrect the life history of a supernova remnant in our own galaxy.

"Cassiopeia A lies in our cosmic backyard and offers the sharpest view of what is left
hundreds of years after a supernova explosion," said Oliver Krause of the Max Planck
Institute for Astronomy in Germany, lead author of a paper about the discovery appearing
in this week's Science. "The echoes of light we found around Cassiopeia A provide us
with a time machine to go back and see its past."

Cassiopeia A is one of the most explored objects in our sky and the subject of more than
1,000 scientific papers. It is the burnt-out corpse of a massive star that ended its life in a
fiery supernova about 11,300 years ago. In fact, until recently, it was the youngest
supernova remnant in our Milky Way galaxy (the new record holder, G1.9+0.3, was
recently discovered using NASA's Chandra X-ray Observatory and other ground-based
telescopes). Because Cassiopeia A is 11,000 light-years from Earth, the light from its
explosion would have reached Earth, sweeping right past it, about 300 years ago.

Astronomers had thought this supernova light was never to be seen again, until 2005,
when Krause and his colleagues discovered hints of it still bouncing around clouds
surrounding the remnant (http://www.spitzer.caltech.edu/Media/releases/ssc2005-
14/index.shtml ). Using Spitzer's infrared eyes, they found so-called infrared echoes,
which occur when a flash of light from the supernova blasts through clouds, heating them
up and causing them to glow in infrared. As the light rolls outward, the infrared echoes
continue to flare up and travel away from the star (see new movie of this effect at

http://www.nasa.gov/mission_pages/spitzer/multimedia/20080529-anim.html).

In the new study, the astronomers used Cassiopeia A's infrared echoes to hone in on faint
visible-light echoes with Subaru and other ground-based telescopes. Visible-light echoes,
known simply as light echoes, occur when visible light from the supernova scatters off
dust. Unlike infrared echoes, they are direct signals from the graves of exploded stars,
bearing all the information about the nature of the original blast.

Next, the astronomers had to act quickly because these echoes can fade within weeks.
They used Subaru's spectrometer instrument to break the light apart and reveal signatures
of atoms present when Cassiopeia A exploded. The resulting spectrum of light revealed
hydrogen and helium -- telltale signs that Cassiopeia A was once a huge red supergiant
star whose core collapsed in a rare supernova referred to as Type IIb. Previously,
scientists did not know the supernova class to which Cassiopeia A belonged.

"This is an exciting result," said Alex Filippenko of the University of California,
Berkeley, a supernova expert not affiliated with the study. "Cassiopeia A has been
studied extensively with many telescopes over a wide range of wavelengths. It is
gratifying that we finally know what kind of star exploded so long ago."

The findings also offer insight into another mystery shrouding Cassiopeia A. When
Cassiopeia A's original star erupted, the event should have been widely witnessed on
Earth as a bright star lighting up the sky. The most likely possible sighting is by the
Astronomer Royal John Flamsteed in 1680, but he made just one observation of a dim
star. The fact that almost no one saw the event is a classic problem in supernova lore.

Now that astronomers have learned how Cassiopeia A was forged, they think they might
know why its death went unnoticed. "Type IIb supernovas fade quickly," said co-author
George Rieke of the University of Arizona in Tucson. "This, plus a few cloudy nights,
might explain the historical enigma around Cassiopeia A."

Recently, astronomers using Chandra, ESA's XMM-Newton Observatory and the Gemini
Observatory in Chile, were able to use light echoes to identify the origins of a supernova
outside our galaxy. That study, together with the new one, demonstrates the power of
light echoes for conjuring up the "ghosts" of long-dead stars.

Other co-authors include Stephan Birkmann and Miwa Goto of the Max Planck Institute
for Astronomy; Tomonori Usuda and Takashi Hattori of the National Astronomical
Observatory of Japan in Hawaii; and Karl Misselt of the University of Arizona. NASA's
Jet Propulsion Laboratory, Pasadena, Calif., manages the Spitzer Space Telescope
mission for NASA's Science Mission Directorate, Washington. Science operations are
conducted at the California Institute of Technology, also in Pasadena. For more
information about Spitzer, visit http://www.spitzer.caltech.edu/spitzer and

http://www.nasa.gov/spitzer . For more information about Subaru, operated by the
National Astronomical Observatory of Japan, visit

http://subarutelescope.org .

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NASA's Phoenix Spacecraft Commanded to Unstow Arm

MEDIA RELATIONS OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109 TELEPHONE 818-354-5011
http://www.jpl.nasa.gov

Guy Webster 818-354-5011
Jet Propulsion Laboratory, Pasadena, Calif.
Guy.webster@jpl.nasa.gov

Dwayne Brown 202-358-1726
NASA Headquarters, Washington
Dwayne.c.brown@nasa.gov

Sara Hammond 520-626-1974
University of Arizona, Tucson
shammond@lpl.arizona.edu

NEWS RELEASE: 2008-087 May 28, 2008

NASA's Phoenix Spacecraft Commanded to Unstow Arm

Scientists leading NASA's Phoenix Mars mission from the University of Arizona in
Tucson sent commands to unstow its robotic arm and take more images of its landing site
early today.

The Phoenix lander sent back new sharp color images from Mars late yesterday. Phoenix
imaging scientists made a color mosaic of images taken by the lander's Surface Stereo
Imager on landing day, May 25, and the first two full "sols," or Martian days, after
landing.

The panorama, now about one-third complete, shows a fish-eye perspective from the
camera, a view from the lander itself all the way to the horizon. Phoenix adjusts its color
vision with "Caltargets," calibrated color targets on disks mounted on the landing deck.
Its color vision isn't quite like human color vision, but close.

"These images are very exciting to the science team," said the Surface Stereo Imager co-
investigator Mark Lemmon of Texas A&M University. "We see the polygons we're
looking for, and we're very excited to fill in the context with more site pan images that go
beyond the workspace." Images to complete the panorama are planned today and
tomorrow, Sols 3 and 4, Lemmon said.

"We appear to have landed where we have access to digging down a polygon trough the
long way, digging across the trough, and digging into the center of a polygon. We've
dedicated this polygon as the first national park system on Mars -- a "keep out" zone
until we figure out how best to use this natural Martian resource," Lemmon said.

Phoenix will use its robotic arm to dig first in another area seen in the panorama, an area
outside the preserved polygon.

Robotic arm manager Bob Bonitz of NASA's Jet Propulsion Laboratory, Pasadena, Calif.,
explained how the arm is to be unstowed today. "It's a series of seven moves, beginning
with rotating the wrist to release the forearm from its launch restraint. Another series of
moves releases the elbow from its launch restraints and moves the elbow from
underneath the biobarrier."

The robotic arm is a critical part of the Phoenix Mars mission. It is needed to trench into
the icy layers of northern polar Mars and deliver samples to instruments that will analyze
what Mars is made of, what its water is like, and whether it is or has ever been a possible
habitat for life.

"Phoenix is in perfect health," JPL's Barry Goldstein, Phoenix project manager, said
Wednesday morning, May 28.

The robotic arm's first movement was delayed by one day when Tuesday's commands
from Earth did not get all the way to the Phoenix lander on Mars. The commands went to
NASA's Mars Reconnaissance Orbiter as planned, but the orbiter's Electra UHF radio
system for relaying commands to Phoenix temporarily shut off. Without new commands,
the lander instead carried out a set of activity commands sent Monday as a backup.
Images and other information from those activities were successfully relayed back to
Earth by the Mars Reconnaissance Orbiter Tuesday evening.

Wednesday morning's uplink to Phoenix and evening downlink from Phoenix were
planned with NASA's Mars Odyssey orbiter as the relay. "We are using Odyssey as our
primary link until we have a better understanding of what happened with Electra,"
Goldstein said.

The Phoenix mission is led by Peter Smith at the University of Arizona with project
management at JPL and development partnership at Lockheed Martin, Denver.
International contributions come from the Canadian Space Agency; the University of
Neuachatel, Switzerland; the universities of Copenhagen and Aarhus, Denmark; Max
Planck Institute, Germany; and the Finnish Meteorological Institute.
For more about Phoenix, visit http://www.nasa.gov/phoenix and

http://phoenix.lpl.arizona.edu.

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Strange Ring Found Circling Dead Star

MEDIA RELATIONS OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109 TELEPHONE 818-354-5011

http://www.jpl.nasa.gov

Whitney Clavin 818-354-4673
Jet Propulsion Laboratory, Pasadena, Calif.
whitney.clavin@jpl.nasa.gov

NEWS RELEASE: 2008-086 May 28, 2008

Strange Ring Found Circling Dead Star

Pasadena, Calif. -- NASA's Spitzer Space Telescope has found a bizarre ring of material
around the magnetic remains of a star that blasted to smithereens.

The stellar corpse, called SGR 1900+14, belongs to a class of objects known as
magnetars. These are the cores of massive stars that blew up in supernova explosions, but
unlike other dead stars, they slowly pulsate with X-rays and have tremendously strong
magnetic fields.

"The universe is a big place and weird things can happen," said Stefanie Wachter of
NASA's Spitzer Science Center at the California Institute of Technology, Pasadena, who
found the ring serendipitously. "I was flipping through archived Spitzer data of the
object, and that's when I noticed it was surrounded by a ring we'd never seen before."
Wachter is lead author of a paper about the findings in this week's Nature. You can see
the ring at http://www.nasa.gov/mission_pages/spitzer/multimedia/20080528.html .

Wachter and her colleagues think that the ring, which is unlike anything ever seen before,
formed in 1998 when the magnetar erupted in a giant flare. They believe the crusty
surface of the magnetar cracked, sending out a flare, or blast of energy, that excavated a
nearby cloud of dust, leaving an outer, dusty ring. This ring is oblong, with dimensions of
about seven by three light-years. It appears to be flat, or two-dimensional, but the
scientists said they can't rule out the possibility of a three-dimensional shell.

"It's as if the magnetar became a huge flaming torch and obliterated the dust around it,
creating a massive cavity," said Chryssa Kouveliotou, senior astrophysicist at NASA's
Marshall Space Flight Center, Huntsville, Ala., and a co-author of the paper. "Then the
stars nearby lit up a ring of fire around the dead star, marking it for eternity."

The discovery could help scientists figure out if a star's mass influences whether it
becomes a magnetar when it dies. Though scientists know that stars above a certain mass
will "go supernova," they do not know if mass plays a role in determining whether the
star becomes a magnetar or a run-of-the-mill dead star. According to the science team,
the ring demonstrates that SGR 1900+14 belongs to a nearby cluster of young, massive
stars. By studying the masses of these nearby stars, the scientists might learn the
approximate mass of the original star that exploded and became SGR 1900+14.

"The ring has to be lit up by something, otherwise Spitzer wouldn't have seen it," said
Enrico Ramirez-Ruiz of the University of California, Santa Cruz. "The nearby massive
stars are most likely what's heating the dust and lighting it up, and this means that the
magnetar, which lies at the exact center of the ring, is associated with the massive star-
forming region."

Rings and spheres are common in the universe. Young, hot stars blow bubbles in space,
carving out dust into spherical shapes. When stars die in supernova explosions, their
remains are blasted into space, forming short-lived beautiful orbs called supernova
remnants. Rings can also form around exploded stars whose expanding shells of debris
ram into pre-existing dust rings, causing the dust to glow, as is the case with the
supernova remnant called 1987A.

But the ring around the magnetar SGR 1900+14 fits into none of these categories. For
one thing, supernova remnants and the ring around 1987A cry out with X-rays and radio
waves. The ring around SGR 1900+14 only glows at specific infrared wavelengths that
Spitzer can see.

At first, the astronomers thought the ring must be what's called an infrared echo. These
occur when an object sends out a blast wave that travels outward, heating up dust and
causing it to glow with infrared light. But when they went back to observe SGR 1900+14
later, the ring didn't move outward as it should have if it were an infrared echo.

A closer analysis of the pictures later revealed that the ring is most likely a carved-out
cavity in a dust cloud -- a phenomenon that must be somewhat rare in the universe since
it had not been seen before. The scientists plan to look for more of these rings.

"This magnetar is still alive in many ways," said Ramirez-Ruiz. "It is interacting with its
environment, making a big impact on the young star-forming region where it was born."

Other paper authors include V. Dwarkadas of the University of Chicago, Ill.; J. Granot of
the University of Hertfordshire, England; S.K. Patel of the Optical Sciences Corporation,
Huntsville, Ala.; and D. Figer of the Rochester Institute of Technology, N.Y. NASA's Jet
Propulsion Laboratory, Pasadena, Calif., manages the Spitzer mission for NASA's
Science Mission Directorate, Washington. Science operations are conducted at the
Spitzer Science Center. Caltech manages JPL for NASA. Spitzer's infrared array camera,
which made the observations, was built by NASA's Goddard Space Flight Center,
Greenbelt, Md. Its principal investigator is Giovanni Fazio of the Harvard-Smithsonian
Center for Astrophysics. For more information about Spitzer, visit

http://www.spitzer.caltech.edu/spitzer and http://www.nasa.gov/spitzer .

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NASA Satellites Illuminate Pollution's Influence on Clouds, Climate

MEDIA RELATIONS OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109 TELEPHONE 818-354-5011
http://www.jpl.nasa.gov

Alan Buis 818-354-0474
Jet Propulsion Laboratory, Pasadena, Calif.
Alan.buis@jpl.nasa.gov

Lynn Chandler 301-286-2806
NASA Goddard Space Flight Center, Greenbelt, Md.
lynn.chandler-1@nasa.gov

NEWS RELEASE: 2008-085 May 27, 2008

NASA Satellites Illuminate Pollution's Influence on Clouds, Climate

PASADENA, Calif. -- Using data from instruments in a constellation of NASA satellites,
scientists have discovered that they can see deep inside of clouds. The satellites are taking first-
of-a-kind measurements, shedding new light on the link between clouds, pollution and rainfall.

Jonathan Jiang of NASA's Jet Propulsion Laboratory, Pasadena, Calif., and colleagues used
sensors from multiple satellites in the Afternoon Constellation, more commonly called the A-
Train, to find that South American clouds infused with airborne pollution -- classified as
"polluted clouds" -- tend to produce less rain than their "clean" counterparts during the region's
dry season. Details of the findings are presented today at the American Geophysical Union's 2008
Joint Assembly in Fort Lauderdale, Fla.

"The A-Train is providing a new way to examine cloud types," said Mark Schoeberl, A-Train
project scientist at NASA's Goddard Space Flight Center, Greenbelt, Md.

Discovery of the link between rain and pollution was possible due to near-simultaneous
measurements from the A-Train satellites. "Typically, it is very hard to get a sense of how
important the effect of pollution on clouds is," said Anne Douglass, deputy project scientist at
Goddard for NASA's Aura satellite. "With the A-Train, we can see the clouds every day and
we're getting confirmation on a global scale that we have an issue here."

Jiang's team used the JPL-developed and managed Microwave Limb Sounder on the A-Train's
Aura satellite to measure the level of carbon monoxide in clouds. The presence of carbon
monoxide implies the presence of smoke and other aerosols, which usually come from the same
emission source, such a power plant or agricultural fire.

With the ability to distinguish between polluted and clean clouds, the team next used Aqua's
Moderate Resolution Imaging Spectroradiometer to study how ice particle sizes change when
aerosol pollution is present in the clouds. The team also used NASA's Tropical Rainfall
Measuring Mission satellite to measure the amount of precipitation falling from the polluted and
clean clouds. All three measurements together show the relationship between pollution, clouds
and precipitation.

The team found that polluted clouds suppressed rainfall during the June-to-October dry season in
South America, which is also a period of increased agricultural burning. During that period it was
more difficult for the measurably smaller ice particles in aerosol-polluted clouds to grow large
enough to fall as rain.

This trend turned up seasonal and regional differences, however, and aerosol pollution was
found, on average, to be less of a factor during the wet monsoon seasons in South America and in
South Asia. Other physical effects, such as large-scale dynamics and rainy conditions that clear
the air of aerosol particles, might also be at play, the researchers suggest.

"The complexity of interactions between aerosols and clouds poses difficult problems that no one
satellite instrument can solve," said Jiang. "But when you put parameters from multiple satellites
all together, you will find much more information than from a single instrument alone."

The five satellites of the A-Train -- NASA's Aqua, Aura, CloudSat, Cloud-Aerosol Lidar and
Infrared Pathfinder Satellite Observation (Calipso) and the French Space Agency's Polarization
and Anisotropy of Reflectances for Atmospheric Sciences coupled with Observations from a
Lidar, or Parasol -- orbit only eight minutes apart and can be thought of as an extended satellite
observatory, providing unprecedented information about clouds, aerosols and atmospheric
composition.

For information about NASA and agency programs, visit: http://www.nasa.gov/home . For
information about the Microwave Limb Sounder on Aura, visit: http://mls.jpl.nasa.gov/ .

JPL is managed for NASA by the California Institute of Technology in Pasadena.

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NASA Mars Lander Prepares to Move Arm

MEDIA RELATIONS OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109 TELEPHONE 818-354-5011
http://www.jpl.nasa.gov

Guy Webster 818-354-5011
Jet Propulsion Laboratory, Pasadena, Calif.
guy.webster@jpl.nasa.gov

Dwayne Brown 202-358-1726
NASA Headquarters, Washington
dwayne.c.brown@nasa.gov

Sara Hammond 520-626-1974
University of Arizona, Tucson
shammond@lpl.arizona.edu

NEWS RELEASE: 2008-084 May 27, 2008

NASA Mars Lander Prepares to Move Arm

NASA's Phoenix Lander is ready to begin moving its robotic arm, first unlatching its
wrist and then flexing its elbow.

Mission scientists are eager to move Phoenix's robotic arm, for that arm will deliver
samples of icy terrain to their instruments made to study this unexplored Martian
environment.

The team sent commands for moving the arm on Tuesday morning, May 27, to NASA's
Mars Reconnaissance Orbiter for relay to Phoenix. However, the orbiter did not relay
those commands to the lander, so arm movement and other activities are now
planned for Wednesday. The orbiter's communication-relay system is in a standby mode.
NASA's Mars Odyssey orbiter is available for relaying communications between Earth and
Phoenix.

NASA's Mars Reconnaissance Orbiter did send back spectacular first images of the landed
Phoenix from orbit, views from the Phoenix lander of where it will work for the next three
months, and a preliminary weather report.

A newly processed image from the high-resolution camera known as HiRISE on NASA's
Mars Reconnaissance Orbiter shows a full-resolution view of the Phoenix parachute and
lander during its May 25 descent, with Heimdall crater in the background.

"Phoenix appears to be descending into the 10 kilometer, or 6-mile, crater, but is actually
20 kilometers, or about 12 miles, in front of the crater," said HiRISE principal investigator
Alfred S. McEwen of the University of Arizona, Tucson.

HiRISE has taken a new color image of Phoenix on the ground about 22 hours after
it landed. It shows the parachute attached to the back shell, the heat shield and the lander
itself against red Mars. The parachute and lander are about 300 meters, roughly 1,000 feet,
apart.

Commands to be sent to the lander Wednesday morning include taking more pictures of
the surroundings and making the first movements of the mission's crucial robotic arm.

A covering that had shielded the arm from microbes during its last few months before
launch had not fully retracted on landing day, May 25, but it moved farther from the arm
during the following day.

"The biobarrier had relaxed more and allows more clearance, but it was not a major
concern either way," said Fuk Li, manager of the Mars Exploration Program
at NASA's Jet Propulsion Laboratory, Pasadena, Calif.

During the next three months, the arm will dig into soil near the lander and deliver samples
of soil and ice to laboratory instruments on the lander deck. Following today's commands,
its movements will begin with unlatching the wrist, then moving the arm upwards in a
stair-step manner.

Phoenix principal investigator Peter Smith of the University of Arizona was delighted with
new images of the workspace. "The workspace is ideal for us because it looks very
diggable. We're very happy to see just a few rocks scattered in the digging area."

The Phoenix weather station, provided by the Canadian Space Agency, was activated
within the first hour after landing on Mars, and measurements are now being recorded
continuously. The data from the first 18 hours after landing have been transmitted back to
the science team, and they have provided a weather report. The temperature ranged
between a minimum of minus 80 degrees Celsius (minus 112 degrees Fahrenheit) in the
early morning and a maximum of minus 30 degrees Celsius (minus 22 degrees Fahrenheit)
in the afternoon. The average pressure was 8.55 millibars, which is less than a hundredth
of the sea level pressure on Earth. The wind speed was 20 kilometers per hour (13 miles
per hour), out of the northeast. The skies were clear. More instruments will be activated
over the coming days, and the weather report will expand to include measurements of
humidity and visibility.

Smith presented a new Surface Stereo Imager view of the American flag and a mini-DVD
on the Phoenix's deck, about three feet above the Martian surface. The mini-DVD from the
Planetary Society contains a message to future Martian explorers, science fiction stories
and art inspired by the Red Planet, and the names of more than a quarter million
Earthlings.

The Phoenix mission is led by Smith at the University of Arizona with project
management at JPL and development partnership at Lockheed Martin. International
contributions come from the Canadian Space Agency; the University of Neuchatel,
Switzerland; the universities of Copenhagen and Aarhus, Denmark; Max Planck Institute,
Germany; and the Finnish Meteorological Institute. More Phoenix information is at

http://www.nasa.gov/phoenix .

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