Geologists have come up with two measurements of radioactive decay to calculate when the Earth's core separated from its crust, but the problem is, these two numbers don't match. Researchers from the University of Bristol think that the giant collision that occurred early on in Earth's history - which went on to form the Moon - might have reset one of these "countdown clocks" and created the discrepancy.

A Russian Kosmos 3M launcher blasted off from the Plesetsk Cosmodrome this morning carrying a satellite designed and built by European university students. The Student Space Exploration and Technology Initiative (SSETI Express) satellite is about the size of a washing machine, and contains several detectors and experiments. Students working in 23 different university groups came together through the Internet to design and build the satellite.

This image is a mosaic of 15 photographs of Saturn's rings taken by Cassini. The strange ripples are caused by gravity from Saturn's moon Prometheus interacting with the ring particles. The ring particles closer to Prometheus move slower than the other particles, which gives the ring this ripple effect.

The massive Large Binocular Telescope, mounted atop Mount Graham in Arizona achieved a major milestone on October 12 with its first images - known as first light. The telescope is so powerful because it combines the light from its twin 8.4 metre mirrors to act as a single 11.8 metre observatory. And its adaptive optics system, which compensates for atmospheric disturbance, makes it even more powerful.

Eleven teams competed in two competitions over the weekend to test technologies for space elevators: beam-powered climbers and new ribbon materials. The climbers needed to scale a 61-metre (200 foot) ribbon within a time limit. Although one climber reached 12 metres (40 feet), it wasn't enough to win the $50,000 prize. In the ribbon competition, competitors needed to create a material that was 50% stronger than the house tether. One team came close, but it wasn't enough. Tougher challenges will be back next year with bigger prizes.

Venus Express was all set to launch, but ESA engineers discovered that small particles were contaminating the spacecraft, so the liftoff was pushed back. Engineers removed the spacecraft from its upper stage booster, opened up the fairing, and discovered that insulation material from the fairing had fallen onto the spacecraft. Fortunately, the pieces of material are large enough to see and remove with tweezers and vacuum cleaners. Once removal is complete, the spacecraft and booster will be reassembled and prepped for launch - before its launch window closes on November 24.

Greetings, fellow SkyWatchers... I'd once again like to express my thanks to the hundreds who took the time to write. This week we'll begin south as we have a look at the NGC 253. Mars isn't the only planet out there, but it's at its best! We'll have a look at planetary nebulae and discuss single stars - as well as try for a challenging comet and asteroid. So, head out under the stars...

Because here's what's up!

Everyone has their own personal reason for taking up astronomy. Some want to make it a career. Others need to satisfy their curiosity. Then there are those who simply get captured by the seductive beauty of the stars. Jan DeBlieu is one of the later. In her book, Year of the Comets she shares her experiences after being entranced by the night skies and at the same time being challenged by her everyday life on Earth.

Anton Nel took this star trail image of the South Celestial Pole in mid-August from Witsand ("White Sands") Nature Reserve in the Northern Cape Province of South Africa. Anton used a Canon 300X and did a 60 minute exposure.

Do you have photos you'd like to share? Post them to the Universe Today astrophotography forum or email them to me directly, and I might feature one in Universe Today.

My guest today is an amateur astrophotographer named Tom Davis. Those of you who subscribe to the Universe Today newsletter should be familiar with his photographs, as I've featured several of them in the last few months. Tom is an amazingly skilled astrophotographer, and he's got some decent equipment. And I'm happy to inform you that the price for this kind of technology is more affordable than it's every been, so if you've ever wanted to get into this hobby, maybe you'll get inspired. Before you start listening, please take a moment to look at his website at: http://www.tvdavisastropics.com.

Andrzej Baran took this beautiful picture of the Northern Lights above the Skibotn Observatory, close to Tromso, Norway - the most northern astronomical observatory in the world. Andrzej used a Canon EOS 300 analog camera with ISO 200 Fuji color slides.

Do you have photos you'd like to share? Post them to the Universe Today astrophotography forum or email them to me directly, and I might feature one in Universe Today.

NASA scientists have found evidence that Mars once had plate tectonics reshaping its surface. Data from Mars Global Surveyor has been stitched together to create a planetary map of magnetism. This map shows striping, where two plates were once pushed apart by new molten lava coming up from under the surface. This new lava become magnetized in the direction of Mars magnetic field at the time. Since this magnetic field flipped several times through the planet's history, the stripes provide a record of when Mars' plates were active.

NASA's Spitzer Space Telescope has spotted what could be the early stages of planets forming around a failed star. The infrared telescope detected clumps of microscopic dust grains and tiny crystals orbiting five brown dwarfs. Similar material has been seen around other newly forming stars and in our own Solar System. Despite being colder and smaller than stars like our Sun, it appears that brown dwarfs still undergo many of the same stages, including the construction of planets.

For the most part, Titan is an alien world with methane rain, lakes of hydrocarbons, and very little that reminds us of Earth. But Saturn's moon has strangely familiar clouds that hover above its middle latitudes. Scientists from the University of Arizona studied Cassini images of some clouds, and watched how they evolved over the course of 3 hours. The clouds rise quickly like thunderstorms here on Earth and then seem to dissipate, as if they're turning into rain.

A Titan 4B rocket carrying a classified cargo for the National Reconnaissance Office blasted off from Vandenberg Air Force Base today. It's believed that the rocket was carrying a next generation reconnaissance satellite. This was the last launch of the Titan 4 class of vehicles. Future launches will use Atlas 5 and Boeing Delta 4 EELVs.

NASA has turned the Hubble Space Telescope at our closest neighbour to help scout out potential landing sites. In addition to being incredibly powerful, Hubble is sensitive to ultraviolet light, which is reflected off of surface materials on the lunar surface. This will allow scientists to identify areas abundant in titanium and iron oxides, which would provide oxygen and metals for future lunar bases. Hubble's resolution is still only 50-100 metres, so it can't reveal Apollo spacecraft still on the Moon.

Get your telescope ready, as the planet Mars is about to put on another fine show. The Red Planet has been getting closer, and will make its closest approach on October 29/30, 2005. Although it won't as close as two years ago, it takes a fairly powerful telescope to be able to tell the difference. Look to the eastern horizon after 8:0pm to see Mars, which will be climbing night after night during October. There's really nothing else that bright that you'd be able to confuse it with.

Just a few days ago, Wilma was a tropical storm, but now it has exploded into a Category 5 hurricane - with the lowest pressure ever recorded in an Atlantic storm. Wilma's pressure was measured early Wednesday at just 882 millibars, breaking the previous record of 888 set in 1988 by Hurricane Gilbert. Wilma is currently off the coast Mexico's Yucatan peninsula , but it's expected to take a sharp right turn and move up through the Florida panhandle on Saturday.

This just blew my mind. Tom Gwilym from Renton, WA took this series of pictures of the space shuttle Atlantis (STS-112) docked to the International Space Station. The blurry pictures are the actual photos of the linkup, and the clear pictures are computer recreations to show their positions.

Do you have photos you'd like to share? Post them to the Universe Today astrophotography forum or email them to me directly, and I might feature one in Universe Today.