Author: Nancy Atkinson

News today from the National Science Foundation will have an impact on how scientists are able to study…. well, impacts. A team of geologists has developed a new way of determining the size and frequency of meteorites that have collided with Earth in the past. By studying sediments found on the ocean floor and looking for isotopes of the rare element osmium, scientists can now figure out not only when a meteorite impact occurred in Earth’s history, but also the size of the meteorite. One of the most exciting benefits of this new technique is the potential for identifying previously unknown impacts.

When meteorites collide with Earth, they carry a different osmium isotope ratio than the levels normally seen throughout the oceans.

“The vaporization of meteorites carries a pulse of this rare element into the area where they landed,” says Rodey Batiza of the National Science Foundation, which funded the research. “The osmium mixes throughout the ocean quickly. Records of these impact-induced changes in ocean chemistry are then preserved in deep-sea sediments.”

François Paquay, a geologist at the University of Hawaii at Manoa analyzed samples from two sites where core samples of the ocean floor were taken, one near the equatorial Pacific and another located off of the tip of South Africa. He measured osmium isotope levels during the late Eocene period, a time during which large meteorite impacts are known to have occurred.

“The record in marine sediments allowed us to discover how osmium changes in the ocean during and after an impact,” says Paquay.

The scientists believe this new approach to estimating impact size will become an important complement to a more well-known method based on iridium.

Paquay’s team also used this method to make estimates of impact size at the Cretaceous-Tertiary (K-T) boundary 65 million years ago. Since the osmium carried by meteorites is dissolved in seawater, the geologists were able to use their method to estimate the size of the K-T meteorite as four to six kilometers in diameter. The meteorite was the trigger, scientists believe, for the mass extinction of dinosaurs and other life forms.

But Paquay doesn’t believe this method will work for events larger than the K-T impact. With such a large meteorite impact, the meteorite contribution of osmium to the oceans would overwhelm existing levels of the element, making it impossible to sort out the osmium’s origin.
But it will be interesting to follow this to see if new, unknown impacts in Earth’s history can be discovered.

Original News Source: Eureka Alert

When it rains space news from Russia, it pours. Not only did the news break today about the Russian Space Agency’s plans to send monkeys to Mars, but also, Russia wants to build an Earth-orbiting factory to build large, interplanetary ships that might be too large to launch from Earth. Additionally, Roscosmos, the Russian space agency said that beginning in 2010, they will likely terminate ferrying space tourists to the International Space Station.

According to the head of Roscosmos Anatoly Perminov, the space agency proposed building a manned assembly complex in Earth orbit and the Russian Security Council supported the idea in an April 11, 2008 meeting. No word on exactly when an orbiting spaceship assembly line would be constructed, but Perminov said it likely wouldn’t be built until after the ISS is completed, which they said would be about 2020. Also, no word if the interplanetary ships will be built for humans or monkeys.

As far as curtailing the program that brings space tourists to the ISS, the Perminov said the increase in crew size on the ISS from the current three members to six in 2009, and then the proposed retirement of the space shuttle in 2010, will put “growing pressure” on the Russian Soyuz spacecraft that carries crews and supplies to the space station. Perminov said they will no longer accept proposals from space tourists, adding that space tourism shouldn’t interfere with scientific research. Roscosmos teamed up with the company Space Adventures beginning in 2001 to bring tourists to the ISS, which seemed to be a fairly lucrative program for the cash-strapped Russian space agency. Existing contracts to bring tourists to the station will be fulfilled, Perminov said.

Dennis Tito became the first space tourist in 2001 when he paid $20 million to ride the Soyuz for a week-long stay on the ISS. The next (and sixth) tourist will be game developer Richard Garriott, scheduled for a Soyuz flight in October 2008.

Original News Source: Lenta Ru (translated)

Looking towards a May 25 landing for the Phoenix Mars Lander, the navigation team for mission adjusted the flight path for the spacecraft on April 10. “This is our first trajectory maneuver targeting a specific location in the northern polar region of Mars,” said Brian Portock, chief of the Phoenix navigation team at the Jet Propulsion Laboratory. The mission’s two prior trajectory maneuvers, made last August and October, put the spacecraft on target to just intersect with Mars. But this recent maneuver put it on course to land at a site called “Green Valley,” a broad, flat valley in Mars north polar region. NASA announced they have “conditionally” approved this site, but a final decision has yet to be made. And why, you ask, hasn’t a final decision been made on a landing site at this late date?

Phoenix mission managers are still looking for a safe, yet exciting place to land. The proposed landing area is an ellipse about 62 miles by about 12 miles (100 kilometers by 20 kilometers). In looking at high resolution images of this area, researchers have mapped more than five million rocks in and around that ellipse, each big enough to end the mission if hit by the spacecraft during landing. “The environmental risks at landing — rocks and slopes — represent the most significant threat to a successful mission. There’s always a chance that we’ll roll snake eyes, but we have identified an area that is very flat and relatively free of large boulders,” said JPL’s David Spencer, Phoenix deputy project manager and co-chair of the landing site working group.

MRO’s High Resolution Imaging Science Experiment (HiRISE) camera has taken more than three dozen images of the area. Analysis of those images prompted the Phoenix team to shift the center of the landing target 13 kilometers (8 miles) southeastward, away from slightly rockier patches to the northwest. Navigators used that new center for planning the recent trajectory correction maneuver.

“Our landing area has the largest concentration of ice on Mars outside of the polar caps. If you want to search for a habitable zone in the arctic permafrost, then this is the place to go,” said Peter Smith, principal investigator for the mission, at the University of Arizona , Tucson .

When Phoenix lands, it will dig to an ice-rich layer expected to lie within arm’s reach of the surface. It will analyze the water and soil for evidence about climate cycles and investigate whether the environment there has been favorable for microbial life.

The April 10 trajectory adjustment began by pivoting Phoenix 145 degrees to orient and then fire spacecraft thrusters for about 35 seconds, then pivoting Phoenix back to point its main antenna toward Earth. The mission has three more planned opportunities for maneuvers before May 25 to further refine the trajectory for a safe landing at the desired location.

In the final seven minutes of its flight on May 25, Phoenix must perform a challenging series of actions to safely decelerate from nearly 21,000 kilometers per hour (13,000 mph). The spacecraft will release a parachute and then use pulse thrusters at approximately 914 meters (3,000 feet) from the surface to slow to about 8 kilometers per hour (5 mph) and land on three legs.

For more information about Phoenix , visit NASA’s site, and ASU’s site

A Cuneiform clay tablet that has puzzled researchers for over 150 years is now believed to describe an asteroid impact in 3123 BC in Austria. Researchers believe the tablet, which seemingly describes a cataclysmic event, may account for the biblical tale of Sodom and Gomorrah. No mention of pillars of salt however, on the clay tablet.

Geologists discovered evidence of a giant landslide centered at Köfels, Austria back in the 19th century. At 500 meters thick and five kilometers in diameter, this landslide mystified researchers trying to figure out why such an event occurred. Some researchers thought the landslide may have been caused by a meteorite impact, because of the evidence of crushing pressures and explosions. But there was no crater, so it didn’t look as an impact site should, and the impact theory fell out of favor. But researchers knew this wasn’t just an ordinary landslide.

But new research brings the impact theory back into play. It centers on another 19th century mystery, a Cuneiform tablet in the British Museum, known as “the Planisphere”. It was found in the remains of the library in the Royal Place at Nineveh, and was made by an Assyrian scribe around 700 BC. It is an astronomical work with drawings of constellations and the text has known constellation names. The clay tablet has attracted a lot of attention but until now no one has come up with a convincing explanation as to what it is.

Alan Bond and Mark Hempsell from Bristol University used computer programs to simulate trajectories and reconstruct the night sky thousands of years ago to establish what the Planisphere tablet refers to. It is a copy of the night notebook of a Sumerian astronomer as he records the events in the sky before dawn on the 29 June 3123 BC (Julian calendar). Half the tablet records planet positions and cloud cover, but the other half of the tablet records an object large enough for its shape to be noted even though it is still in space. The astronomer made an accurate note of its trajectory relative to the stars, which to an error better than one degree is consistent with an impact at Köfels.

The observation suggests the asteroid is over a kilometer in diameter and the original orbit about the Sun was an Aten type, a class of asteroid that orbits close to the earth, that is resonant with the Earth’s orbit. This trajectory explains why there is no crater at Köfels. The incoming angle was very low (six degrees) and means the asteroid clipped a mountain near the town of Längenfeld, 11 kilometers from Köfels, and this caused the asteroid to explode before it reached its final impact point. As it travelled down the valley it became a fireball, about five kilometers in diameter (the size of the landslide). When it hit Köfels it created enormous pressures that pulverized the rock and caused the landslide but because it was no longer a solid object it did not create a classic impact crater.

Mark Hempsell, hinting at the possible fate of Sodom and Gomorrah, added, “Another conclusion can be made from the trajectory. The back plume from the explosion (the mushroom cloud) would be bent over the Mediterranean Sea re-entering the atmosphere over the Levant, Sinai, and Northern Egypt. The ground heating though very short would be enough to ignite any flammable material – including human hair and clothes. It is probable more people died under the plume than in the Alps due to the impact blast.”

This evidence seems to coincide with the biblical story of the legendary dens of vice (“Then the Lord rained down burning sulfur on Sodom and Gomorrah – from the Lord out of the heavens” – Genesis 19:24) but it’s never been categorically proven that the towns actually existed in their suspected location close to the Dead Sea. And the story of Lot’s wife turning into a pillar of salt for turning around to witness the mayhem is just biblical legend as well.

The full translation of the tablet together with the analysis supporting these conclusions can be found in the book, “A Sumerian Observation of the Kofels’ Impact Event” by Bond and Hempsell.

Original News Sources: Bristol University and The Register