NASA’s photo of the day the Earth smiled

November 13, 2013

NASA's caption:  On July 19, 2013, in an event celebrated the world over, NASA's Cassini spacecraft slipped into Saturn's shadow and turned to image the planet, seven of its moons, its inner rings -- and, in the background, our home planet, Earth. Image Credit:  NASA/JPL-Caltech/SSI

NASA’s caption: On July 19, 2013, in an event celebrated the world over, NASA’s Cassini spacecraft slipped into Saturn’s shadow and turned to image the planet, seven of its moons, its inner rings — and, in the background, our home planet, Earth. Image Credit: NASA/JPL-Caltech/SSI

It’s difficult to improve on NASA’s matter-of-fact explanations.

The Day the Earth Smiled

On July 19, 2013, in an event celebrated the world over, NASA’s Cassini spacecraft slipped into Saturn’s shadow and turned to image the planet, seven of its moons, its inner rings — and, in the background, our home planet, Earth.

With the sun’s powerful and potentially damaging rays eclipsed by Saturn itself, Cassini’s onboard cameras were able to take advantage of this unique viewing geometry. They acquired a panoramic mosaic of the Saturn system that allows scientists to see details in the rings and throughout the system as they are backlit by the sun. This mosaic is special as it marks the third time our home planet was imaged from the outer solar system; the second time it was imaged by Cassini from Saturn’s orbit; and the first time ever that inhabitants of Earth were made aware in advance that their photo would be taken from such a great distance.

With both Cassini’s wide-angle and narrow-angle cameras aimed at Saturn, Cassini was able to capture 323 images in just over four hours. This final mosaic uses 141 of those wide-angle images. Images taken using the red, green and blue spectral filters of the wide-angle camera were combined and mosaicked together to create this natural-color view. A brightened version with contrast and color enhanced, a version with just the planets annotated, and an unannotated version are also available.

This image spans about 404,880 miles (651,591 kilometers) across.

The outermost ring shown here is Saturn’s E ring, the core of which is situated about 149,000 miles (240,000  kilometers) from Saturn. The geysers erupting from the south polar terrain of the moon Enceladus supply the fine icy particles that comprise the E ring; diffraction by sunlight gives the ring its blue color. Enceladus (313 miles, or 504 kilometers, across) and the extended plume formed by its jets are visible, embedded in the E ring on the left side of the mosaic.

At the 12 o’clock position and a bit inward from the E ring lies the barely discernible ring created by the tiny, Cassini-discovered moon, Pallene (3 miles, or 4 kilometers, across). (For more on structures like Pallene’s ring, see PIA08328). The next narrow and easily seen ring inward is the G ring. Interior to the G ring, near the 11 o’clock position, one can barely see the more diffuse ring created by the co-orbital moons, Janus (111 miles, or 179 kilometers, across) and Epimetheus (70 miles, or 113 kilometers, across). Farther inward, we see the very bright F ring closely encircling the main rings of Saturn.

Following the outermost E ring counter-clockwise from Enceladus, the moon Tethys (662 miles, or 1,066 kilometers, across) appears as a large yellow orb just outside of the E ring. Tethys is positioned on the illuminated side of Saturn; its icy surface is shining brightly from yellow sunlight reflected by Saturn. Continuing to about the 2 o’clock position is a dark pixel just outside of the G ring; this dark pixel is Saturn’s Death Star moon, Mimas (246 miles, or 396 kilometers, across). Mimas appears, upon close inspection, as a very thin crescent because Cassini is looking mostly at its non-illuminated face.

The moons Prometheus, Pandora, Janus and Epimetheus are also visible in the mosaic near Saturn’s bright narrow F ring. Prometheus (53 miles, or 86 kilometers, across) is visible as a faint black dot just inside the F ring and at the 9 o’clock position. On the opposite side of the rings, just outside the F ring, Pandora (50 miles, or 81 kilometers, across) can be seen as a bright white dot. Pandora and Prometheus are shepherd moons and gravitational interactions between the ring and the moons keep the F ring narrowly confined. At the 11 o’clock position in between the F ring and the G ring, Janus (111 miles, or 179 kilometers, across) appears as a faint black dot. Janus and Prometheus are dark for the same reason Mimas is mostly dark: we are looking at their non-illuminated sides in this mosaic.  Midway between the F ring and the G ring, at about the 8 o’clock position, is a single bright pixel, Epimetheus. Looking more closely at Enceladus, Mimas and Tethys, especially in the brightened version of the mosaic, one can see these moons casting shadows through the E ring like a telephone pole might cast a shadow through a fog.

In the non-brightened version of the mosaic, one can see bright clumps of ring material orbiting within the Encke gap near the outer edge of the main rings and immediately to the lower left of the globe of Saturn. Also, in the dark B ring within the main rings, at the 9 o’clock position, one can see the faint outlines of two spoke features, first sighted by NASA’s Voyager spacecraft in the early 1980s and extensively studied by Cassini.

Finally, in the lower right of the mosaic, in between the bright blue E ring and the faint but defined G ring, is the pale blue dot of our planet, Earth. Look closely and you can see the moon protruding from the Earth’s lower right. (For a higher resolution view of the Earth and moon taken during this campaign, see PIA14949.) Earth’s twin, Venus, appears as a bright white dot in the upper left quadrant of the mosaic, also between the G and E rings.  Mars also appears as a faint red dot embedded in the outer edge of the E ring, above and to the left of Venus.

For ease of visibility, Earth, Venus, Mars, Enceladus, Epimetheus and Pandora were all brightened by a factor of eight and a half relative to Saturn. Tethys was brightened by a factor of four. In total, 809 background stars are visible and were brightened by a factor ranging from six, for the brightest stars, to 16, for the faintest. The faint outer rings (from the G ring to the E ring) were also brightened relative to the already bright main rings by factors ranging from two to eight, with the lower-phase-angle (and therefore fainter) regions of these rings brightened the most. The brightened version of the mosaic was further brightened and contrast-enhanced all over to accommodate print applications and a wide range of computer-screen viewing conditions.

Some ring features — such as full rings traced out by tiny moons — do not appear in this version of the mosaic because they require extreme computer enhancement, which would adversely affect the rest of the mosaic. This version was processed for balance and beauty.

This view looks toward the unlit side of the rings from about 17 degrees below the ring plane. Cassini was approximately 746,000 miles (1.2 million kilometers) from Saturn when the images in this mosaic were taken. Image scale on Saturn is about 45 miles (72 kilometers) per pixel.

This mosaic was made from pictures taken over a span of more than four hours while the planets, moons and stars were all moving relative to Cassini. Thus, due to spacecraft motion, these objects in the locations shown here were not in these specific places over the entire duration of the imaging campaign. Note also that Venus appears far from Earth, as does Mars, because they were on the opposite side of the sun from Earth.

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, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.

For more information about the Cassini-Huygens mission visit http://www.nasa.gov/cassini and http://saturn.jpl.nasa.gov .

Image credit: NASA/JPL-Caltech/SSI

Bigger image:

Cassini's view looking back from Saturn, on July 19, 2013, the day the Earth smiled. Click for much larger view.  NASA photo and annotations

Cassini’s view looking back from Saturn, on July 19, 2013, the day the Earth smiled. Click for much larger view. NASA photo and annotations

What do you think:  Tax money well spent?

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Gold medal to NASA and JPL: Mars mission succeeds against overwhelming odds

August 6, 2012

Curiosity is on the ground.

What were the odds?  What did NASA and Jet Propulsion Laboratories (JPL) need to overcome?   Watch this:

Did that astonshingly Rube Goldberg-looking set of devices work?

Here’s the news, from NBC’s science editor Alan Boyle:

PASADENA, Calif. — After eight years of planning and eight months of interplanetary travel, NASA’s Mars Science Laboratory pulled off a touchdown of Super Bowl proportions, all by itself. It even sent pictures from the goal line.

The spacecraft plunged through Mars’ atmosphere, fired up a rocket-powered platform and lowered the car-sized, 1-ton Curiosity rover to its landing spot in 96-mile-wide (154-kilometer-wide) Gale Crater. Then the platform flew off to its own crash landing, while Curiosity sent out a text message basically saying, “I made it!”

That message was relayed by the orbiting Mars Odyssey satellite back to Earth. A radio telescope in Australia picked up the message and sent it here to NASA’s Jet Propulsion Laboratory. When the blips of data appeared on the screens at JPL’s mission control, the room erupted in cheers and hugs.

Congratulations!  We need good news, and this is great news.

So far as I can tell, no U.S. television network covered the event live in Pasadena.  What a shame.

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Annals of Global Warming: NOAA team finds oceans heated up since 1993

May 21, 2010

News from NOAA and NASA:

The upper layer of the world’s ocean has warmed since 1993, indicating a strong climate change signal, according to a new study. The energy stored is enough to power nearly 500 100-watt light bulbs per each of the roughly 6.7 billion people on the planet.

“We are seeing the global ocean store more heat than it gives off,” said John Lyman, an oceanographer at NOAA’s Joint Institute for Marine and Atmospheric Research, who led an international team of scientists that analyzed nine different estimates of heat content in the upper ocean from 1993 to 2008.

John Lyman and Gregory Johnson show instruments used to measure ocean temperature - NOAA photo, 2010

From NOAA: John Lyman (left) holds an expendable bathythermograph or XBT, a device that was dropped from ships to obtain temperature. Gregory Johnson (right) holds an ARGO Float, an autonomous, free-floating ocean device that collects a variety of data, including temperature. (NOAA photo, 2010)

The team combined the estimates to assess the size and certainty of growing heat storage in the ocean. Their findings will be published in the May 20 edition of the journal Nature. The scientists are from NOAA, NASA, the Met Office Hadley Centre in the United Kingdom, the University of Hamburg in Germany and the Meteorological Research Institute in Japan.

“The ocean is the biggest reservoir for heat in the climate system,” said Josh Willis, an oceanographer at NASA’s Jet Propulsion Laboratory and one of the scientists who contributed to the study. “So as the planet warms, we’re finding that 80 to 90 percent of the increased heat ends up in the ocean.”

A warming ocean is a direct cause of global sea level rise, since seawater expands and takes up more space as it heats up. The scientists say that this expansion accounts for about one-third to one-half of global sea level rise.

Combining multiple estimates of heat in the upper ocean – from the surface to about 2,000 feet down – the team found a strong multi-year warming trend throughout the world’s ocean. According to measurements by an array of autonomous free-floating ocean floats called ARGO as well as by earlier devices called expendable bathythermographs or XBTs that were dropped from ships to obtain temperature data, ocean heat content has increased over the last 16 years.

The team notes that there are still some uncertainties and some biases.

“The XBT data give us vital information about past changes in the ocean, but they are not as accurate as the more recent Argo data,” said Gregory Johnson, an oceanographer at NOAA’s Pacific Marine Environmental Laboratory. “However, our analysis of these data gives us confidence that on average, the ocean has warmed over the past decade and a half, signaling a climate imbalance.”

Data from the array of Argo floats­ – deployed by NOAA and other U.S. and international partners ­– greatly reduce the uncertainties in estimates of ocean heat content over the past several years, the team said. There are now more than 3,200 Argo floats distributed throughout the world’s ocean sending back information via satellite on temperature, salinity, currents and other ocean properties.

NOAA’s mission is to understand and predict changes in the Earth’s environment, from the depths of the ocean to the surface of the sun, and to conserve and manage our coastal and marine resources. Visit us on Facebook.

Note: Full name of the paper is Robust Warming of the Global Upper Ocean. Authors are John M. Lyman, Joint Institute for Marine and Atmospheric Research, University of Hawaii at Manoa and NOAA/Pacific Marine Environmental Laboratory, Seattle; Simon A. Good, Met Office Hadley Centre; Viktor V. Gouretski Klima Campus, University of Hamburg; Masayoshi Ishii, Climate Research Department, Meteorological Research Institute, Japan; Gregory C. Johnson, NOAA/Pacific Marine Environmental Laboratory, Seattle; Matthew D. Palmer, Met Office Hadley Centre; Doug M. Smith, Met Office Hadley Centre; and Josh K. Willis, NASA Jet Propulsion Laboratory, Pasadena, Calif.

Map showing 3,200 free-floating Argo floats, instruments used to measure ocean temperature - International Argo Project

From NASA: The international science team analyzed nine different estimates of heat content in the upper ocean, based on ocean temperature data from a global array of more than 3,200 Argo free-floating profiling floats and longer data records from expendable bathythermographs dropped from ships. Image credit: International Argo Project

Resources:

Update, February 16, 2011: Interesting that this research got so little play in mainstream media, more curious that those who contend global warming and/or the need to do anything about it have buried it so well.  RealClimate noted that denialist Larry Bell, writing in Forbes, even cited the work of this team, but claiming a contrary resultEven Watts Up appears to have gone silent on this after a curtain-raiser post on the project.  Odd.


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