The biggest mass extinction in the Earth's history happened approximately 250 million years ago. During the "Great Dying", more than 90% of creatures in the ocean, and 75% of life on land went extinct. What caused the extinction is still up for debate, but a researcher from the University of Washington thinks that low levels of oxygen in the atmosphere sure didn't help. Oxygen went down to 12% (currently it's 21%), and this made standing at sea level the same as being atop a 5,300 metre mountain (17,000 feet).

Now firmly in orbit, the European Space Agency's SMART-1 is seeking out a spot at the Moon's north pole that could be bathed in constant sunlight. Scientists are predicting that there's a spot, a few square kilometres in size across that is constantly heated by the sun, and would be the perfect spot for a lunar base. Finding the area is difficult, though, because we don't get a good view from Earth, and the shadows in this region are very long and can obscure the details.

NASA's Opportunity rover has lost the ability to steer its right-front wheel, making it more difficult for controllers to maneuver it around on the surface of Mars. The problem happened on April 13 (sol 433) when the rover was executing a turn - its wheel stuck at a slight angle. The rover has continued to travel since the problem happened, and can make observations, but it's more difficult to make precise movements.

The Chandra X-Ray Observatory spent 150 hours examining supernova remnant G21.5-0.9, revealing a beautiful ghostly shell. The shell is created by the shockwave of particles ejected by the supernova explosion as they slam into material that was sloughed off earlier by the star. This shockwave heats the surrounding material to millions of degrees causing it to blaze in the X-ray spectrum visible to Chandra. The star that produced this explosion was probably 10 times larger than the Sun.

Since its formation billions of years ago, Mars has never been a perfectly spherical planet. Even now, the planet has the huge Tharsis Bulge on one side of the planet, where volcanic activity raised up vast region several kilometres above the surrounding plain. These instabilities have caused the planet to wobble on its orbit, obscuring its original orientation. A Canadian researcher has traced 5 impact craters which came from a single object that broke up as it struck the planet, defining the planet's original poles and equator.

Researchers from UC Berkeley have looked into the past to confirm that a fundamental aspect of the Universe - the fine structure constant, or alpha - has remain unchanged for at least 7 billion years. This constant shows up in many formulae dealing with electricity and magnetism, and helps describe how radiation is emitted by atoms. This conflicts with a recent announcement from Australian researchers that described a change in alpha over time.

Let's say you're browsing around the comic book store and happened to notice a perfect copy of Action Comics #1 on the rack mixed in with the current stuff. It's in mint condition, untouched since it was first printed almost 70 years ago. Now imagine the same situation... except with stars. Anna Frebel is a PhD student at the Research School of Astronomy & Astrophysics at the Australian National University. She's working with a team of astronomers who have found the oldest star ever seen - possibly untouched since shortly after the Big Bang.

Oh, yeah. There's a Moon - but it's going to do some great tricks as it leads the way to the M44, shows us an Apollo landing site, offers a variety of observing challenges, occults Jupiter and Eta Virginis, and even has a penumbral eclipse! This week provides an opportunity to view bright double stars, enjoy some "colors" and even catch a "falling star". So get out those binoculars and telescopes, because...

Here's what's up!

NASA's DART mission, which launched on Friday to test automated docking techniques, was prematurely shut down on Saturday when the spacecraft ran out of fuel. DART launched perfectly on board a Pegasus XL rocket and reached within 90 meters of its target, an inactive satellite already in orbit. It was supposed to make several close approaches to the satellite, but it didn't even have enough propellant for one pass. Mission controllers aborted the mission and fired its deorbit rockets to put it into a decaying orbit where it will burn up. An investigation team has been assigned to figure out what went wrong.

Scientists have been watching a huge iceberg called B-15A, after it split away from Antarctica almost 5 years ago. After drifting along the coast of the continent, it finally smashed into the 70 km Drygalski ice tongue, breaking off a large chunk. The ice tongue is such a well known feature of Antarctica that it appears on many maps (they'll need to be revised). B-15A, on the other hand, appears totally unaffected by the collision, and will continue to grind away at the tongue.

The newest residents of the International Space Station arrived at their destination on Saturday, as their Soyuz TMA-6 capsule docked automatically. Hatches between the spacecraft and station were opened a few hours later, and the three crew members joined the two men of Expedition 10 on board the station. Commander Sergei Krikalev and astronaut John Phillips will remain on the station until October 2005, while ESA Astronaut Roberto Vittori will return in about a week with Leroy Chiao and Salizhan Sharipov.

Here's a relief. Instead of being painfully stretched (aka spaghettified) by the immense tidal forces around a black hole, you'd probably just be roasted by the intense heat. Professor Andrew Hamilton at the University of Colorado predicts that only the smallest black holes would actually stretch you out like this. All the larger, supermassive black holes are already choking on enough material, that their surrounding environment is a superhot plasma heated to millions of degrees and blasting out intense radiation.

Michael Griffin addressed NASA employees on Thursday, when he became the 11th Administrator for the space agency. In his address, Griffin said he would focus on getting the shuttles ready to return to flight, and continue to fulfill the Vision for Space Exploration, which sees astronauts returning to the Moon and eventually continuing on to Mars in the coming decades. Griffin was nominated by President Bush on March 14, and was confirmed by the Senate on April 13.

The 11th crew to man the International Space Station blasted off from the Baikonur Cosmodrome on Thursday. The Soyuz TMA capsule carrying Cosmonaut Sergei Krikalev, Astronaut John Phillips, and European Space Agency Astronaut Roberto Vittori of Italy reached orbit a few minutes after launch. Krikalev and Phillips will replace the current crew, while Vittori will only remain on the station for a week and then return with Expedition 10. The Soyuz will dock on Saturday.

NASA's Cassini spacecraft captured this beautiful image of Saturn's moon Enceladus perched just above the giant planet's rings. Enceladus is 505 km (314 miles) across, and the photo was taken when Cassini was just below the ring plane. Saturn's A, B, and C rings are also visible in the photograph.

When astronomers discovered that the planets around Upsilon Andromedae had very strange orbits, they weren't sure what could have caused it. Researchers from Berkeley and Northwestern have developed a simulation that shows how an additional planet could have given the other planets the orbital kick they needed to explain their current eccentricities. If a similar planet had passed through our own Solar System early on, all our planets could be in wildly different orbits around the Sun.