Archive for August, 2014
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August 5th, 2014
Credit: ESA
The European Space Agency’s Rosetta spacecraft was launched in 2004 and will arrive at comet 67P/Churyumov-Gerasimenko on August 6 – a 10 year long voyage.
It will be the first mission in history to rendezvous with a comet, escort it as it orbits the Sun, and deploy a lander to its surface.
Rosetta is an ESA mission with contributions from its member states and NASA.
Image of comet 67P/Churyumov-Gerasimenko.
Credits: ESA/Rosetta/NAVCAM
After completing a complex series of nine orbital maneuvers since the end of hibernation on January 20, Rosetta is finally in position to rendezvous with the comet.
A timeline of the most crucial steps leading to Rosetta’s arrival at its target comet on Wednesday includes: Orbit entry on August 6, triggered by a small but crucial thruster firing lasting 6 minutes 26 seconds.
That burn will start at 09:00 GMT (11:00 CEST). The commands were uploaded during the night of August 4.
This burn will tip Rosetta into the first leg of a series of three-legged triangular paths about the comet. The legs will be about 100 km long and it will take Rosetta between three and four days to complete each one.
Main Control Room at ESOC, ESA’s operations centre in Darmstadt, Germany.
Credit: ESA-J.Mai
Mission operations and science teams at ESA and scientists from multiple countries will be following progress closely.
Tune in to a Livestream of arrival activities starting August 6 at 08:00UTC.
Go to: http://rosetta.esa.int
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Image Credit:
NASA/JPL-Caltech/MSSS
The message from those steering NASA’s Curiosity Mars rover is that sandy Martian valleys are in the rover’s near future!
NASA’s Curiosity Mars rover has just crossed one stretch of rocks hazardous to its wheels and may soon reach rocks different from any it has examined so far.
As it approaches the second anniversary of its landing on Mars –10:32 p.m. PDT, Aug. 5, 2012 — the rover is also approaching its first close look at bedrock that is part of Mount Sharp, the layered mountain in the middle of Mars’ Gale Crater.
Damage to Curiosity’s aluminum wheels from driving across similar terrain last year prompted a change in route planning to skirt such rock-studded terrain wherever feasible.
The main map here shows the assortment of landforms near the location of NASA’s Curiosity Mars rover as the rover’s second anniversary of landing on Mars nears.
Image Credit:
NASA/JPL-Caltech/Univ. of Arizona
Curiosity spent much of July 2014 crossing an upland area called “Zabriskie Plateau,” where embedded, sharp rocks presented hazards for the rover’s wheels.
An artistic conception of the early Earth, showing a surface pummeled by large impacts, resulting in extrusion of deep-seated magma onto the surface. At the same time, distal portion of the surface could have retained liquid water.
Artwork by Simone Marchi
New research suggests that asteroidal collisions not only severely altered the geology of the “Hadean Earth” (meaning hell-like), but likely played a major role in the subsequent evolution of life on Earth as well.
That Hadean period is pegged at roughly 4.0 to 4.5 billion years ago.
In the very beginning of Earth’s formation, the first 500 million years, that Hadean epoch is a less well-known period. It was assumed that it was wildly hot and volcanic and everything was covered with magma – completely unlike the present day.
Large collisions as late as about four billion years ago may have repeatedly boiled away existing oceans into steamy atmospheres.
How big and how frequent were those incoming bombardments, and what were their effects on the surface of the Earth?
According to Elkins-Tanton, director of the School of Earth and Space Exploration at Arizona State University (ASU), the new research is attempting to bridge that time from the last giant accretionary impact that largely completed the Earth and produced our moon, to today’s current state of affairs – plate tectonics and a habitable surface.
Rate of impactors
Researchers found that on average, Hadean Earth 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.
“Prior to approximately four billion years ago, no large region of Earth’s surface could have survived untouched by impacts and their effects,” says Simone Marchi of NASA’s Solar System Exploration Research Virtual Institute at the Southwest Research Institute. “The new picture of the Hadean Earth emerging from this work has important implications for its habitability,” the scientist noted in an ASU press statement.
“During this time, the lag between major collisions was long enough to allow intervals of more clement conditions, at least on a local scale,” says Marchi. “Any life emerging during the Hadean eon was likely 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.”
An international team of scientists published their findings in the July 31, 2014 issue of Nature.
Go to:
http://www.nature.com/nature/journal/v511/n7511/full/nature13539.html
NOTE: While there, give a listen to a related audio presentation by Simone Marchi that discusses the new bombardment model of the early Earth. It’s located on the right side of the web page.
