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New NASA Research Shows Giant Asteroids Battered Early Earth
July 30, 2014

New research shows that more than four billion years ago the surface of Earth was heavily reprocessed - or melted, mixed, and buried - as a result of giant asteroid impacts. A new terrestrial bombardment model, calibrated using existing lunar and terrestrial data, sheds light on the role asteroid collisions played in the evolution of the uppermost layers of the early Earth during the geologic eon called the "Hadean" (approximately 4 to 4.5 billion years ago).

An international team of researchers from academic and government institutions, including NASA's Solar System Exploration Research Virtual Institute (SSERVI) at NASA's Ames Research Center in Moffett Field, California, published their findings in a paper, "Widespread Mixing and Burial of Earth's Hadean Crust by Asteroid Impacts" in the July 31, 2014 issue of Nature.

"A large asteroid impact could have buried a substantial amount of Earth's crust with impact-generated melt," said Yvonne Pendleton, SSERVI Director at Ames. "This new model helps explain how repeated asteroid impacts may have buried Earth's earliest and oldest rocks."

Terrestrial planet formation models indicate Earth went through a sequence of major growth phases: initially accretion of planetesimals - planetary embryos - over many tens of millions of years, then a giant impact by a large proto-planet that led to the formation of our moon, followed by the late bombardment when giant asteroids several tens to hundreds of miles in size periodically hit ancient Earth, dwarfing the one that killed the dinosaurs (estimated to be six miles in size) only 65 million years ago.

Researchers estimate accretion during the late bombardment contributed less than one percent of Earth's present-day mass, but the giant asteroid impacts still had a profound effect on the geological evolution of early Earth. Prior to four billion years ago Earth was resurfaced over and over by voluminous impact-generated melt. Furthermore, large collisions as late as about four billion years ago may have repeatedly boiled away existing oceans into steamy atmospheres. Despite the heavy bombardment, the findings are compatible with the claim of liquid water on Earth's surface as early as about 4.3 billion years ago based on geochemical data.

The new research reveals that asteroidal collisions not only severely altered the geology of the Hadean eon Earth, but likely also played a major role in the subsequent evolution of life on Earth as well.

"Prior to approximately four billion years ago, no large region of Earth's surface could have survived untouched by impacts and their effects," said Simone Marchi, SSERVI senior researcher at the Southwest Research Institute in Boulder, Colorado, and the paper's lead author. "The new picture of the Hadean Earth emerging from this work has important implications for its habitability."

Large impacts had particularly severe effects on existing ecosystems. Researchers found that on average, Hadean Earth more than four billion years ago could have been hit by one to four impactors that were more than 600 miles wide and capable of global sterilization, and by three to seven impactors more than 300 miles wide and capable of global ocean vaporization.

"During that time, the lag between major collisions was long enough to allow intervals of more clement conditions, at least on a local scale," said Marchi. "Any life emerging during the Hadean eon likely needed to be resistant to high temperatures, and could have survived such a violent period in Earth’s history by thriving in niches deep underground or in the ocean’s crust.”

The research was an international effort led by Marchi and William Bottke from the Southwest Research Institute in Boulder; Linda Elkins-Tanton from Carnegie Institution for Science in Washington; Michael Bierhaus and Kai Wünnemann from the Museum fur Naturkunde in Berlin, Germany; Alessandro Morbidelli from Observatoire de la Côte d'Azur in Nice, France, and David Kring from the Universities Space Research Association and Lunar and Planetary Institute in Houston.

The research was supported in part by SSERVI, a virtual institute that, with international partnerships, brings science and exploration researchers together in a collaborative virtual setting. SSERVI is funded by the Science Mission Directorate and Human Exploration and Operations Mission Directorate at NASA Headquarters in Washington.

For more information about SSERVI and selected member teams, visit:

Rachel Hoover
Ames Research Center, Moffett Field, Calif.

2014 NASA Honor Awards: Congratulations to all Code S honorees!
July 23, 2014

The honorees received their awards at the ceremony on July 23, 2014, in the N201 Main Auditorium.

2014 Ames Honor Award Group/Team Individual Team Names

Pavilion Lake Research Project (PLRP)

NASA Ames Celebrates 75th Anniversary with 'Living Museum'
July 1, 2014

In 1939, nestled between Moffett Field Naval Air Station and the California towns of Mountain View and Sunnyvale, a seed of innovation was planted. Nourished by determination and outside-the-box thinking, that seed has borne fruit in the form of cutting-edge advances in aeronautics and technology, and an in-depth scientific understanding of our Earth and the universe. On December 20, 2014, NASA’s Ames Research Center, Moffett Field. California, turns 75 years old.

To help celebrate the center’s diamond anniversary, Ames, in partnership with Mountain View and Sunnyvale, will display a 17-piece "living museum" highlighting the center's past and present engineering and scientific endeavors at certain businesses and public venues. The exhibits will be in place from July 1 through July 31.

The living museum includes exhibits about the following Ames projects and activities:

For more information about the Ames 75th anniversary celebration living museum, visit:

By Jonas Dino
NASA's Ames Research Center

NASA Begins Testing of New Spectrograph on Agency's Airborne Observatory
June 24, 2014

Astronomers are eagerly waiting to begin use of a new instrument to study celestial objects: a high-resolution, mid-infrared spectrograph mounted on NASA's Stratospheric Observatory for Infrared Astronomy (SOFIA), the world's largest flying telescope.

This new instrument, the Echelon-Cross-Echelle Spectrograph (EXES), can separate wavelengths of light to a precision of one part in 100,000. At the core of EXES is an approximately 3-foot (1 meter) bar of aluminum called an echelon grating, carefully machined to act as 130 separate mirrors that split light from the telescope into an infrared "rainbow."

SOFIA is a heavily modified Boeing 747 Special Performance jetliner that carries a telescope with an effective diameter of about 8-feet (2.5-meters) at altitudes of 39,000 to 45,000 feet (12 to 14 km), above more than 99 percent of Earth's atmospheric water vapor. Lower in the atmosphere, at altitudes associated with most ground-based observatories, water vapor obscures much of what can be learned when viewed in the infrared spectrum.

"The combination of EXES's high spectral resolution and SOFIA's access to infrared radiation from space provides an unprecedented ability to study celestial objects at wavelengths unavailable from ground-based telescopes," said Pamela Marcum, a program scientist at the SOFIA Science Center and Program Office in Moffett Field, California. "EXES on SOFIA will provide data that cannot be obtained by any other astronomical facility on the ground or in space, including all past, present or those observatories now under development."

EXES successfully carried out its first two flights on SOFIA on the nights of April 7 and 9, according to Matthew Richter, leader of the team that is developing the instrument at the University of California, Davis, Physics Department. EXES is a collaboration between U.C. Davis and NASA's Ames Research Center in Moffett Field.

"During the two flights, EXES made observations to investigate and characterize the instrument's performance. All the main goals of these observations were successful, although further commissioning flights are required to test EXES in all of its modes," said Richter.

On the first commissioning flight, EXES observed emissions from Jupiter's atmosphere in two molecular hydrogen lines. These observations will be used to understand how gas rises from deep in Jupiter's interior and mixes into the planet's upper atmosphere.

During the second commissioning flight, EXES observed a young, massive star in the constellation Cygnus that is still embedded in its natal cocoon. The star, known as AFGL 2591, warms up the surrounding interstellar dust and causes ice coatings on the dust to evaporate. The warmed dust provides an excellent background infrared "lamp" to probe the chemical make-up of the intervening gas.

New stars and planets are forming from that material through processes similar to the ones that made the sun and Earth. These observations are designed to study water vapor around the protostar, and demonstrate that EXES can detect absorption from the lowest energy level of water molecules despite interference from water vapor from Earth's atmosphere.

"Of the observations obtained during the instrument's first flights, only one can be done from the ground, albeit with some difficulty, and the others are impossible from even the best ground-based telescope sites because the water in Earth's atmosphere is opaque at these wavelengths," Richter said. "While space observatories are above Earth's atmosphere, the massive optical equipment required to separate the light as finely as EXES does -EXES weighs almost 1,000 pounds -would be a challenge to launch into space. In these observations, the spectral features we are studying are narrow, and finely dividing the infrared spectrum to detect them is exactly what EXES was designed to do."

SOFIA is a joint project of NASA and the German Aerospace Center (DLR). The aircraft is based at and the program is managed from NASA Armstrong Flight Research Center's facility in Palmdale, California. NASA's Ames Research Center, manages the SOFIA science and mission operations in cooperation with the Universities Space Research Association (USRA) headquartered in Columbia, Maryland, and the German SOFIA Institute (DSI) at the University of Stuttgart.

For more information about SOFIA, visit:


By Rachel Hoover
NASA's Ames Research Center

By Steve Cole/Dwayne Brown
Headquarters, Washington

Image Credit: Credit: Lockheed Martin

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