Category Archives: The Moon

Multiple media, Space Science, The Moon

Cassini captures Saturn & Earth, Messenger captures Earth and Moon

I mentioned last week that the Cassini probe at Saturn and the Messenger probe at Mercury would each be taking a picture of earth. NASA has now released the wonderful images NASA Releases Images of Earth Taken by Distant Spacecraft – NASA

Saturn's rings and our planet Earth

The Day the Earth Smiled

In this rare image taken on July 19, 2013, the wide-angle camera on NASA’s Cassini spacecraft has captured Saturn’s rings and our planet Earth and its moon in the same frame. It is only one footprint in a mosaic of 33 footprints covering the entire Saturn ring system (including Saturn itself).  At each footprint, images were taken in different spectral filters for a total of 323 images: some were taken for scientific purposes and some to produce a natural color mosaic.  This is the only wide-angle footprint that has the Earth-moon system in it. Continue…

PASADENA, Calif. — Color and black-and-white images of Earth taken by two NASA interplanetary spacecraft on July 19 show our planet and its moon as bright beacons from millions of miles away in space.

NASA’s Cassini spacecraft captured the color images of Earth and the moon from its perch in the Saturn system nearly 900 million miles (1.5 billion kilometers) away. MESSENGER, the first probe to orbit Mercury, took a black-and-white image from a distance of 61 million miles (98 million kilometers) as part of a campaign to search for natural satellites of the planet.

In the Cassini images Earth and the moon appear as mere dots — Earth a pale blue and the moon a stark white, visible between Saturn’s rings. It was the first time Cassini’s highest-resolution camera captured Earth and its moon as two distinct objects.

It also marked the first time people on Earth had advance notice their planet’s portrait was being taken from interplanetary distances. NASA invited the public to celebrate by finding Saturn in their part of the sky, waving at the ringed planet and sharing pictures over the Internet. More than 20,000 people around the world participated.

“We can’t see individual continents or people in this portrait of Earth, but this pale blue dot is a succinct summary of who we were on July 19,” said Linda Spilker, Cassini project scientist, at NASA’s Jet Propulsion Laboratory in Pasadena, Calif. “Cassini’s picture reminds us how tiny our home planet is in the vastness of space, and also testifies to the ingenuity of the citizens of this tiny planet to send a robotic spacecraft so far away from home to study Saturn and take a look-back photo of Earth.”

Pictures of Earth from the outer solar system are rare because from that distance, Earth appears very close to our sun. A camera’s sensitive detectors can be damaged by looking directly at the sun, just as a human being can damage his or her retina by doing the same. Cassini was able to take this image because the sun had temporarily moved behind Saturn from the spacecraft’s point of view and most of the light was blocked.

A wide-angle image of Earth will become part of a multi-image picture, or mosaic, of Saturn’s rings, which scientists are assembling. This image is not expected to be available for several weeks because of the time-consuming challenges involved in blending images taken in changing geometry and at vastly different light levels, with faint and extraordinarily bright targets side by side.

“It thrills me to no end that people all over the world took a break from their normal activities to go outside and celebrate the interplanetary salute between robot and maker that these images represent,” said Carolyn Porco, Cassini imaging team lead at the Space Science Institute in Boulder, Colo. “The whole event underscores for me our ‘coming of age’ as planetary explorers.”

In the MESSENGER image, Earth and the moon are less than a pixel, but appear very large because they are overexposed. Long exposures are required to capture as much light as possible from potentially dim objects. Consequently, bright objects in the field of view become saturated and appear artificially large.

“That images of our planet have been acquired on a single day from two distant solar system outposts reminds us of this nation’s stunning technical accomplishments in planetary exploration,” said MESSENGER Principal Investigator Sean Solomon of Columbia University’s Lamont-Doherty Earth Observatory in Palisades, N.Y. “And because Mercury and Saturn are such different outcomes of planetary formation and evolution, these two images also highlight what is special about Earth. There’s no place like home.”

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL designed, developed and assembled the Cassini orbiter and its two onboard cameras. The Johns Hopkins University Applied Physics Laboratory in Laurel, Md., designed and built MESSENGER, a spacecraft developed under NASA’s Discovery Program. NASA’s Marshall Space Flight Center in Huntsville, Ala., manages the program for the agency’s Science Mission Directorate in Washington. JPL and APL manage their respective missions for NASA.  The California Institute of Technology in Pasadena manages JPL for NASA.

To view the Earth images. visit: http://go.nasa.gov/1383AHq .

More information about the picture and the Wave at Saturn campaign is available at: http://saturn.jpl.nasa.gov/waveatsaturn .

To view the MESSENGER images, visit: http://go.nasa.gov/16Vnt5G .

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The pair of bright star-like features in the upper panel are not stars at all, but the Earth and Moon! MESSENGER was at a distance of 98 million kilometers (61 million miles) from Earth when this picture was taken. The computer-generated image in the lower left shows how the Earth appeared from Mercury at the time. Much of the Americas, all of Europe and Africa, the Middle East, and much of Asia were visible.

MESSENGER took this image as part of a campaign to search for natural satellites of Mercury. Mercury has no moons that we know of. If any exist, they must be small (less than a few kilometers), or we would have seen them by now. The strategy for the satellite search involves taking multiple images of locations at predetermined distances from Mercury, from 2.5 to 25 times the planet radius. Pictures of these points in space are captured at intervals ranging from seconds to nearly an hour, depending on their distances from Mercury. A moving satellite will appear at different positions in images of the same region of space taken at different times.

Continue…

History, The Moon

Celebrate the Apollo 11 landing today

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Today is the 44th anniversary of the first time a human walked on another world. Check out the site The First Men on the Moon: The Apollo 11 Lunar Landing

Watch, listen, and relive the excitement of the Apollo 11 lunar landing as experienced minute-by-minute by the courageous crew of Apollo 11 and Mission Control.

Here is a gallery of pictures taken by Apollo astronauts: The Best Space Images Ever Were Taken by Apollo Astronauts With Hasselblad Cameras – Wired Science.

This evening we are going to try the ceremony Evoloterra — When We First Left Planet Earth. (Two of the authors recently discussed Evoloterra on The Space Show.)

Moonandback offers an online documentary about the landing: The Journeys Of Apollo: Commemorating The Anniversary Of Apollo 11 Moon Landing – Moonandback

And here is another documentary in full:

Space Science, The Moon

GRAIL spacecraft expose origin of lunar mass concentrations

A release from NASA:

NASA’s Grail Mission Solves Mystery of Moon’s Surface Gravity

PASADENA, Calif. — NASA’s Gravity Recovery and Interior Laboratory (GRAIL) mission has uncovered the origin of massive invisible regions that make the moon’s gravity uneven, a phenomenon that affects the operations of lunar-orbiting spacecraft.

Because of GRAIL’s findings, spacecraft on missions to other celestial bodies can navigate with greater precision in the future.

GRAIL’s twin spacecraft studied the internal structure and composition of the moon in unprecedented detail for nine months. They pinpointed the locations of large, dense regions called mass concentrations, or mascons, which are characterized by strong gravitational pull. Mascons lurk beneath the lunar surface and cannot be seen by normal optical cameras.

GRAIL scientists found the mascons by combining the gravity data from GRAIL with sophisticated computer models of large asteroid impacts and known detail about the geologic evolution of the impact craters. The findings are published in the May 30 edition of the journal Science.

GRAIL Artist Rendition
Using a precision formation-flying technique, the twin GRAIL spacecraft will
map the moon’s gravity field, as depicted in this artist’s rendering. Radio signals
traveling between the two spacecraft provide scientists the exact measurements
required as well as flow of information not interrupted when the spacecraft are at
the lunar farside, not seen from Earth. The result should be the most accurate
gravity map of the moon ever made.

“GRAIL data confirm that lunar mascons were generated when large asteroids or comets impacted the ancient moon, when its interior was much hotter than it is now,” said Jay Melosh, a GRAIL co-investigator at Purdue University in West Lafayette, Ind., and lead author of the paper. “We believe the data from GRAIL show how the moon’s light crust and dense mantle combined with the shock of a large impact to create the distinctive pattern of density anomalies that we recognize as mascons.”

The origin of lunar mascons has been a mystery in planetary science since their discovery in 1968 by a team at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, Calif. Researchers generally agree mascons resulted from ancient impacts billions of years ago. It was not clear until now how much of the unseen excess mass resulted from lava filling the crater or iron-rich mantle upwelling to the crust.

On a map of the moon’s gravity field, a mascon appears in a target pattern. The bulls-eye has a gravity surplus. It is surrounded by a ring with a gravity deficit. A ring with a gravity surplus surrounds the bulls-eye and the inner ring. This pattern arises as a natural consequence of crater excavation, collapse and cooling following an impact. The increase in density and gravitational pull at a mascon’s bulls-eye is caused by lunar material melted from the heat of a long-ago asteroid impact.

“Knowing about mascons means we finally are beginning to understand the geologic consequences of large impacts,” Melosh said. “Our planet suffered similar impacts in its distant past, and understanding mascons may teach us more about the ancient Earth, perhaps about how plate tectonics got started and what created the first ore deposits.”

This new understanding of lunar mascons also is expected to influence planetary geology well beyond that of Earth and our nearest celestial neighbor.

“Mascons also have been identified in association with impact basins on Mars and Mercury,” said GRAIL principal investigator Maria Zuber of the Massachusetts Institute of Technology in Cambridge. “Understanding them on the moon tells us how the largest impacts modified early planetary crusts.”

Launched as GRAIL A and GRAIL B in September 2011, the probes, renamed Ebb and Flow, operated in a nearly circular orbit near the poles of the moon at an altitude of about 34 miles (55 kilometers) until their mission ended in December 2012. The distance between the twin probes changed slightly as they flew over areas of greater and lesser gravity caused by visible features, such as mountains and craters, and by masses hidden beneath the lunar surface.

JPL managed GRAIL for NASA’s Science Mission Directorate in Washington. The mission was part of the Discovery Program managed at NASA’s Marshall Space Flight Center in Huntsville, Ala. NASA’s Goddard Space Flight Center, in Greenbelt, Md., manages the Lunar Reconnaissance Orbiter. Operations of the spacecraft’s laser altimeter, which provided supporting data used in this investigation, is led by the Massachusetts Institute of Technology in Cambridge.

Lockheed Martin Space Systems in Denver built GRAIL.

For more information about GRAIL, visit: http://www.nasa.gov/grail