Sources :: Astrobiology Magazine ⁽¹⁾ :: SwRI press release ⁽²⁾

The impactor believed to have wiped out the dinosaurs and other life forms on Earth some 65 million years ago has been traced back to a breakup event in the main asteroid belt. The finding provides insights into one of the most important extinction events in Earth’s history. Known as the Cretaceous-Tertiary (K-T) extinction, this impact event signaled a dramatic change in the evolutionary history of Earth. Understanding the origins and effects of this event can not only teach us about the past, but can also help us understand how future impacts could alter our planet’s global biosphere.

A joint U.S.-Czech team from Southwest Research Institute (SwRI) and Charles University in Prague suggests that the parent object of asteroid (298) Baptistina disrupted when it was hit by another large asteroid, creating numerous large fragments that would later create the Chicxulub crater on the Yucatan Peninsula as well as the prominent Tycho crater found on the Moon. The team of researchers, including Dr. William Bottke (SwRI), Dr. David Vokrouhlicky (Charles University, Prague) and Dr. David Nesvorny (SwRI), combined observations with several different numerical simulations to investigate the Baptistina disruption event and its aftermath. A particular focus of their work was how Baptistina fragments affected the Earth and Moon.

At approximately 170 kilometers in diameter and having characteristics similar to carbonaceous chondrite meteorites, the Baptistina parent body resided in the innermost region of the asteroid belt when it was hit by another asteroid estimated to be 60 kilometers in diameter. This catastrophic impact produced what is now known as the Baptistina asteroid family, a cluster of asteroid fragments with similar orbits. According to the team’s modeling work, this family originally included approximately 300 bodies larger than 10 kilometers and 140,000 bodies larger than 1 kilometer.

Once created, the newly formed fragments’ orbits began to slowly evolve due to thermal forces produced when they absorbed sunlight and re-radiated the energy away as heat. According to Bottke, “By carefully modeling these effects and the distance traveled by different-sized fragments from the location of the original collision, we determined that the Baptistina breakup took place 160 million years ago, give or take 20 million years.”

The gradual spreading of the family caused many fragments to drift into a nearby “dynamical superhighway” where they could escape the main asteroid belt and be delivered to orbits that cross Earth’s path. The team’s computations suggest that about 20 percent of the surviving multi-kilometer- sized fragments in the Baptistina family were lost in this fashion, with about 2 percent of those objects going on to strike the Earth, a pronounced increase in the number of large asteroids striking Earth.

Support for these conclusions comes from the impact history of the Earth and Moon, both of which show evidence of a two-fold increase in the formation rate of large craters over the last 100 to 150 million years. As described by Nesvorny, “The Baptistina bombardment produced a prolonged surge in the impact flux that peaked roughly 100 million years ago. This matches up pretty well with what is known about the impact record.”

Bottke adds, “We are in the tail end of this shower now. Our simulations suggest that about 20 percent of the present-day, near-Earth asteroid population can be traced back to the Baptistina family.”

The team then investigated the origins of the 180 kilometer diameter Chicxulub crater, which has been strongly linked to the extinction of the dinosaurs 65 million years ago. Studies of sediment samples and a meteorite from this time period indicate that the Chicxulub impactor had a carbonaceous chondrite composition much like the well-known primitive meteorite Murchison. This composition is enough to rule out many potential impactors but not those from the Baptistina family. Using this information in their simulations, the team found a 90 percent probability that the object that formed the Chicxulub crater was a refugee from the Baptistina family.

These simulations also showed there was a 70 percent probability that the lunar crater Tycho, an 85 kilometer crater that formed 108 million years ago, was also produced by a large Baptistina fragment. Tycho is notable for its large size, young age and its prominent rays that extend as far as 1,500 kilometers across the Moon. Vokrouhlicky says, “The probability is smaller than in the case of the Chicxulub crater because nothing is yet known about the nature of the Tycho impactor.”

This study demonstrates that the collisional and dynamical evolution the main asteroid belt may have significant implications for understanding the geological and biological history of Earth.

As Bottke says, “It is likely that more breakup events in the asteroid belt are connected in some fashion to events on the Earth, Moon and other planets. The hunt is on!”

The article, “An asteroid breakup 160 Myr ago as the probable source of the K/T impactor,” was published in the Sept. 6 issue of Nature.

The NASA Origins of Solar Systems, Planetary Geology and Geophysics, and Near-Earth Objects Observations programs funded Bottke’s and Nesvorny’s research; Vokrouhlicky was funded by the Grant Agency of the Czech Republic.

Footnotes:

1. ”The Baptistina Breakup“, Astrobiology Magazine, September 8, 2007 (↩)
2. ”An asteroid breakup 160 Myr ago as the probable source of the K/T impactor“, SwRI, September 6, 2007 (↩)

Flight Engineer Daniel Tani, aboard the International Space Station, became the first American astronaut to lose a close family member while in space this week.

Tani’s wife Jane and Dr. Sean Roden, a flight surgeon at Johnson Space Center in Houston, broke the news of Rose Tani’s death to her son over a face-to-face video conference. The 90-year-old was killed Wednesday when her car was struck by a freight train outside Chicago. In a interview with NPR, Dr. Roden said Tani was taking the news as well as could be expected and would adjust scheduled duties if necessary, although no change had yet been announced.

Tani was supposed to return home next week on the now-delayed STS-122 shuttle mission. Efforts are being made to ensure funeral services are made available in real-time to the astronaut.

NASA today released the following statement regarding the death of Tani’s mother:

 

“The entire NASA family grieves with Dan on the unexpected loss of his mother yesterday. We will work to provide Dan and his family with any assistance that they need during this difficult time.”

You can read Tani’s NASA biography here.

*UPDATE* December 19, 2007
A tanking test of the space shuttle on Tuesday allowed engineers to identify the cause of faulty sensor readings that scrubbed two shuttle launch attempts earlier this month. The tanking test, conducted after shuttle workers added additional instrumentation to the shuttle’s external tank, revealed that electrical connectors that carry data through the wall of the external tank were at fault, and not the sensors themselves. The engine cutoff sensors, designed to determine when the shuttle’s liquid hydrogen fuel is exhausted, generated erroneous data during tests in the hours leading up to launch attempts on December 6 and 9. Tuesday’s tests revealed that the sensors were not at the fault, and the connectors can be accessed while the shuttle remains on the launch pad. Shuttle officials said, however, they were not sure any repair work could be completed in advance of the currently-planned January 10 launch.

December 9, 2007
At T-5 hours 3 minutes, ECO hydrogen sensor #3 failed. 30 minutes later the launch was officially scrubbed. The remainder of the day will be spent further troubleshooting the nagging issues with these fuel sensors. Today’s failure to launch will mean no further attempts will be made during this launch window.

The next launch window opens January 2nd, 2008.

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December 9, 2007
T-5 hours 30 minutes (approximately 9 actual hours) until mission launch and NASA has begun the process of filling the Atlantis’ external tanks with liquid hydrogen and liquid oxygen propellants. It should be during this phase of launch preparations that any issues with the ECO fuel sensors are detected. It was faulty readings from two of the ECO sensors that delayed the STS-122 launch earlier this week. A third sensor failed after the external tank was drained of fuel.The next stage begins at T-3 hours and holding; a built in 2 hour hold process when inertial measurement unit pre-flight calibrations are performed, and Merritt Island Launch Area (MILA) antennas are aligned.Learn more about the countdown process here.

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December 8, 2007
Today’s Mission Management Team meeting has concluded. We are “go” for a Sunday, December 9th launch attempt.

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December 7, 2007
After a Mission Management Team meeting earlier today, NASA announced that the new target launch time for the shuttle Atlantis mission STS-122 will be Sunday, December 9, 3:21pm. The team will meet again Saturday at 1pm to decide whether or not to go ahead with a Sunday launch attempt.There was no word in the NASA press release as to the status of the three fuel sensors that have so far delayed the launch.While we’re all eagerly awaiting Atlantis’ launch, it might be a good time to take a look at what the astronauts are scheduled to accomplish this mission.

About This Video

This video does a nice job of relating the true size of our planet and sun within the Universe.

About This Video (excerpt from YouTube)

The Vision for Space Exploration is the United States space policy announced on January 14, 2004 by U.S. President George W. Bush. It is seen as a response to the Space Shuttle Columbia disaster, the state of human spaceflight at NASA, and a way to regain public enthusiasm for space exploration.

The Vision calls for the space program to:

Complete the International Space Station by 2010
Retire the Space Shuttle by 2010
Develop the Orion spacecraft (formerly known as the Crew Exploration Vehicle) by 2008, and conduct its first human spaceflight mission by 2014
Develop Shuttle Derived Launch Vehicles
Explore the Moon with robotic spacecraft missions by 2008 and crewed missions by 2020
Explore Mars and other destinations with robotic and crewed missions
When the Vision was announced in January 2004, the U.S. Congress and the scientific community gave it a mix of positive and negative reviews. For example, Rep. Dave Weldon (R-Fla.) said, “I think this is the best thing that has happened to the space program in decades,” while physicist and outspoken manned spaceflight opponent Robert L. Park said that robotic spacecraft “are doing so well it’s going to be hard to justify sending a human.”

Others, such as the Mars Society have argued that it makes more sense to avoid going back to the Moon and instead focus on going to Mars first.

In a position paper issued by the National Space Society (NSS), a return to the Moon should be considered a high space program priority, in order to begin development of the knowledge and identification of the industries unique to the Moon. The NSS believes that the Moon may be a repository of the history and possible future of our planet, and that the six Apollo landings only scratched the surface of that treasure.

According to NSS, the Moon’s far side, permanently shielded from the noisy Earth, is an ideal site for future radio astronomy. Unique products may be producible in the nearly limitless extreme vacuum of the lunar surface, and the Moon’s remoteness is the ultimate isolation for biologically hazardous experiments.

Lunar resources include most if not all raw materials available on Earth. The Moon can serve as a proving ground for a wide range of space operations and processes, including developments toward In-Situ Resource Utilization or “living off the land” (i.e., self-sufficiency) for permanent human outposts. This has various benefits.

Initial return missions as recently proposed by the U.S. President and NASA can be done through space operations using the existing launch infrastructure and assets developed by the shuttle and International Space Station programs, plus existing expendable launch vehicles, with a minimum of new research and development programs. The lessons learned from international cooperation during ISS construction and operations can be improved upon and extended to human missions to the Moon, Mars and elsewhere.

Initial missions could place scientific equipment on the Moon and return samples from areas never explored, such as the polar regions. Extent of water and other volatiles important to lunar industrialization could be determined. As future reusable launch systems begin operations, reducing cost and enabling higher flight rates, Earth-Moon traffic can become routine. With humans on the Moon again, NASA’s space activities would take on new vigor and public interest.

Throughout much of 2004, it was unclear whether the U.S. Congress would be willing to approve and fund the Vision for Space Exploration. However, in November 2004, Congress passed an omnibus spending bill which gave NASA the $16.2 billion that President Bush had sought to kick-start the Vision. According to then-NASA chief Sean O’Keefe, that spending bill “was as strong an endorsement [of the space exploration vision] as any of us could have imagined.” In 2005, Congress passed S.1281, the NASA Authorization act of 2005, which explicitly endorses the Vision.

The current NASA Administrator, Michael Griffin, who took office in April 2005, is a big supporter of the Vision, but has also modified it somewhat, saying that he wants to reduce the four year gap between the retirement of the Space Shuttle and the first manned mission of the Crew Exploration Vehicle.

The launch scheduled for August 24, 1985 was scrubbed at T-5 minutes due to thunderstorms in the vicinity. The launch scheduled for August 25 was delayed when the orbiter’s number five on-board general purpose computer failed. The launch on August 27 was delayed three minutes, one second due to a combination of weather and an unauthorized ship entering the restricted solid rocket booster recovery area.

Three communications satellites were deployed: ASC-1, for American Satellite Company; AUSSAT-1, an Australian Communications Satellite; and SYNCOM IV-4, the Synchronous Communications Satellite. ASC-1 and AUSSAT-1 both attached to Payload Assist Module-D (PAM-D) motors. SYNCOM IV-4 (also known as LEASAT-4) failed to function after reaching the correct geosynchronous orbit. Fisher and van Hoften performed two extravehicular activities (EVAs) totaling 11 hours, 51 minutes. Part of time spent retrieving, repairing and redeploying LEASAT-3, which had been deployed on Mission 51-D. Middeck Payload: Physical Vapor Transport Organic Solid Experiment (PVTOS).

The mission shortened one day when the AUSSAT sunshield hung up on remote manipulator system camera and AUSSAT had to be deployed before scheduled.

Mission Highlights

Mission: ASC-1/American Satellite Company, AUSSAT-1/Australian Communications Satellite, SYNCOM IV-4
Space Shuttle: Discovery
Crew Members: Commander Joseph H. Engle, Pilot Richard O. Covey, Mission Specialists James D. A. van Hoften, John M. Lounge and William F. Fisher
Launch Pad: 39A
Launch Weight: 262,309 pounds
Launched: Aug. 27, 1985 at 6:58:01 a.m. EDT
Landing Site: Edwards Air Force Base, Calif.
Landing: Sept. 3, 1985 at 6:15:43 a.m. PDT
Landing Weight: 196,674 pounds
Runway: 23
Rollout Distance: 6,100 feet
Rollout Time: 47 seconds
Revolution: 112
Mission Duration: 7 days, 2 hours, 17 minutes, 42 seconds
Returned to KSC: Sept. 8, 1985
Orbit Altitude: 242 nautical miles
Orbit Inclination: 28.45 degrees
Miles Traveled: 2.9 million

Launch countdown July 12 halted at T-3 seconds after main engine ignition when a malfunction of number two Space Shuttle Main Engine (SSME) coolant valve caused shutdown of all three main engines. Launch July 29 delayed one hour, 37 minutes due to problem with table maintenance block update uplink. Five minutes, 45 seconds into ascent, number one main engine shutdown prematurely, resulting In an Abort To Orbit (ATO) trajectory.

Primary payload was Spacelab-2. Despite abort-to-orbit, which required mission replanning, the mission declared success. A special part of modular Spacelab system, the Igloo, located at head of three-pallet train, provided on-site support to instruments mounted on pallets. The main mission objective was to verify performance of Spacelab system sand determine interface capability of the orbiter, and measure environment induced by spacecraft. Experiments covered life sciences, plasma physics, astronomy, high energy astrophysics, solar physics, atmospheric physics and technology research.

The flight marked the first time the ESA Instrument Pointing System (IPS) was tested in orbit. This unique experiment pointing enstrument was designed with an accuracy of one arc second. Initially, some problems were experienced when it was commanded to track the Sun. A series of software fixes were made and the problem was corrected.

Mission Highlights

Mission: Spacelab-2
Space Shuttle: Challenger
Crew Members: Commander Gordon Fullerton,Pilot Roy D. Bridges, Mission Specialists F. Story Musgrave, Anthony W. England, Karl G. Henize, and Payload Specialists Loren W. Acton, John-David F. Bartoe
Launch Pad: 39A
Launch Weight: 252,855 pounds
Launched: July 29, 1985, 5:00:00 p.m. EDT
Landing Site: Edwards Air Force Base, Calif.
Landing: August 6, 1985, 12:45:26 p.m. PDT
Landing Weight: 216,735 pounds
Runway: 23
Rollout Distance: 8,569 feet
Rollout Time: 55 seconds
Mission Duration: 7 days, 1 hour, 38 minutes, 52 seconds
Orbit Altitude: 173 nautical miles
Orbit Inclination: 49.5 degrees
Miles Traveled: 3,2 million

Three communications satellites, all attached to the Payload Assist Module-D (PAM-D) motors, were deployed: MORELOS-A, for Mexico; ARABSAT-A, for Arab Satellite Communications Organization; and TELSTAR-3D, for AT&T. Also flown: deployable/retrievable Shuttle Pointed Autonomous Research Tool for Astronomy (SPARTAN-1); six Get Away Special canisters; Strategic Defense Initiative experiment called the High Precision Tracking Experiment (HPTE); a materials processing furnace called Automated Directional Solidification Furnace (ADSF); and two French biomedical experiments.

Mission Highlights

Mission: MORELOS-A, ARABSAT-A and TELSTAR-3D Communications Satellites
Space Shuttle: Discovery
Crew Members: Commander Daniel C. Brandenstein, Pilot John O. Creighton, Mission Specialists Shannon W. Lucid, John M. Fabian, Steven R. Nagel and Payload Specialists Patrick Baudry and Sultan Salman Al-Saud
Launch Pad: 39A
Launch Weight: 256,524 pounds
Launched: June 17, 1985 at 7:33:00 a.m. EDT
Landing Site: Edwards Air Force Base, Calif.
Landing: June 24, 1985 at 6:11:52 a.m. PDT
Landing Weight: 204,169 pounds
Runway: 23
Rollout Distance: 7,433 feet
Rollout Time: 42 seconds
Revolution: 112
Mission Duration: 7 days, 1 hour, 38 minutes, 52 seconds
Orbit Altitude: 209 nautical miles
Orbit Inclination: 28.45 degrees
Miles Traveled: 2.9 million