Researchers at Washington University in St. Louis have used primitive meteorites called chondrites to develop a model of the Earth's early atmosphere. And it looked nothing like what we have today. Instead of the familiar oxygen and nitrogen, our early atmosphere would have been a toxic mixture of methane, ammonia, hydrogen and water vapour. Simulating this early environment was actually quite difficult to calculate because the minerals of the early Earth reacted to the hot environment in hard-to-predict ways.

Cassini scientists have assembled this mosaic image of a region on Titan called Fensal-Aztlan. The northern part of the region, "Fensal", has small islands which range in size from 5 to 40 km (3 to 25 miles) across, while the southern "Aztlan" region mostly lacks these islands. The "islands" are thought to be raised areas of water ice, surrounded by dark particulate material which came out of the atmosphere.

The Planetary Fourier Spectrometer (PFS) on board the ESA's Mars Express spacecraft malfunctioned a few months ago, and the agency wants to know why. The instrument was working perfectly for two years, and made the surprising discovery of methane in Mars' atmosphere. It might be malfunctioning because of spacecraft vibration, but the source of the problem is still under investigation. Even if engineers can't get the instrument working again, the spacecraft still has another 6 which are working fine.

Although astronomers have discovered plenty of comets, they've always thought it was just a fraction (less than 3%) of the number of comets out there - and one of them might have our names on it. Fortunately, this scenario doesn't seem so likely, according to new research from scientists at the Australian National University, astronomers have probably found more like 20% of comets. That means that small comets, capable of destroying a city, probably only hit the Earth once every 40 million years, and big continent-busting comets probably only hit us once every 150 million years.

The Hubble Space Telescope used its Advanced Camera for Surveys to capture this beautiful photograph of the Boomerang Nebula. This cloud of dust and gas has two nearly symmetric cones of material coming out of it. It was created through a process called bipolar outflow, where a dying star ejects material as it spins. It could be that the star is surrounded by a disk of dust, so only the top and bottom material can escape, or a powerful magnetic field is shaping it as it escapes.

Down here on Earth we're protected by our planet's magnetic field from harmful radiation, but out in space, it gets a lot more dangerous. One particularly dangerous region are the Earth's Van Allen belts which astronauts have to pass through to get to the Moon and beyond. Researchers working in Antarctica have observed two rare space storms which drained electrons out of the Van Allen belt, and reformed it closer to Earth in a region that was thought to be free of radiation. This research will help scientists predict what kinds of solar storms will move this radiation around, and give astronauts time to prepare if they're caught in the open.

An unpiloted Progress cargo ship docked to the Zvezda module of the International Space Station on Saturday, delivering supplies to the crew of Expedition 11. The supplies include food, water, fuel, oxygen, air, clothing and experimental hardware. Also on board are spare parts for the Russian Vozdukh carbon dioxide removal system and the Elektron oxygen generator. The astronaut will try and repair the Elektron next week to bring it back into service.

Greetings, fellow SkyWatchers! This week is a sure sign of the Fall season as we welcome back the "Harvest Moon". While Selene will be the major focus of our studies this week, we can still take the opportunity to enjoy double star Gamma Delphini, find out why Vega is so "hot", and have a look at variable Beta Lyrae. So, head out under the moonlit skies, because ...

Here's what's up!

What is your computer doing when you're not using it? If your answer is "nothing", then you need to put it to work in the name of science - finding aliens, detecting gravity waves, or predicting asteroid paths. Join the Universe Today and Bad Astronomy team, and compete with other teams worldwide to see who can help crunch the most data. We'd love to get your help.

September arrives and with it come all the sweet memories of anticipation, trepidation and expectation of new school years. These days, I relive these feelings through my children but many of my own emotions still lie close to the surface. There won't be any astronomy texts yet for my two young ones, but others may find on their list the introductory text by Andrew Fraknoi, David Morrison, and SidneyWolff entitled Voyages to the Stars and Galaxies. For those so fortunate, a good memory may be more practical than a sweet memory, for this book is chalkfull of pertinent astronomical information.

How will the Universe end? Right now cosmologists have two equally distressing scenarios mapped out for the long term fate of the Universe. On the one hand, gravity might slow down the expansion of our Universe so that it coasts to a stop and possibly even collapses back down into a Big Crunch. On the other hand, the expansion of the Universe could continue indefinitely thanks to the acceleration of dark energy. We would face a cold, lonely future as other galaxies fade away into the distance. My guest today is Eric Linder from the Lawrence Berkeley National Laboratory and he's proposing experiments that could help us learn which of these two fates await us.

Saturn's moon Titan has long held a special fascination to astrobiologists. Its thick atmosphere is largely composed of nitrogen and organic molecules which are the building blocks of life. At a frigid -178 C (-289 F), however, it's much too cold to support life. But there could be some habitable locations on Titan, you just have to look carefully. Methane clouds around Titan indicate that it probably has an active cycle similar to the water cycle here on Earth. There could be areas where get warm enough on Titan for life to gain a foothold.

The time frame for the formation of new planets appears to be getting shorter than previously believed. Astronomers have discovered gaps in protoplanetary disks that suggest there are gas giants forming there. One star, GM Aurigae, is a younger version of our own Sun and the gap in its disk is at about the same location as our own gas giant planets. Since GM Aurigae is only 1 million years old, these results challenge the traditional theories that planets slowly formed over many millions of years.

An Italian team of astronomers have found a gamma ray burst that blew up 12.7 billion light-years away - the most distant ever seen. Astronomers have calculated that it exploded with 300 times more energy than our Sun will put out in its entire 10+ billion year lifespan. The blast was discovered by NASA's Swift satellite, which is dedicated to discovering these powerful explosions.

Astronomers have spotted a dusty disc around an old, dead star. This star is similar to what our own star will look like billions of years from now. What's unusual, however, is this dust cloud. It should have disappeared long ago; either sucked into the star, or blasted away by intense radiation. One theory is that a planet is still orbiting the dead star, and is continuously shedding material to create this dust.

The frame-filling view of Saturn's moon Rhea was taken by Cassini on August 1, 2005. Although in this image, Rhea looks quite similar to our Moon or the planet Mercury, it's actually covered in thick ice which would melt if it ever got as close to the Sun as Mercury. Rhea is 1,528 kilometers (949 miles) across, and you can see one of its larger craters, Izanagi, near the middle of the moon.

When humans return to the Moon in the next decade, they'll be facing a dangerous combination of cosmic rays and solar flares. Astronauts will need to avoid getting too much radiation, so NASA is working to better understand risks. The upcoming Lunar Reconnaissance Orbiter (LRO) will carefully measure and map the Moon's radiation environment. It will also have a special instrument designed to simulate how this radiation will affect the human body.

When Deep Impact excavated a crater in Comet Tempel 1, it released a spew of material that has existed since our Solar System first formed, billions of years ago. By analyzing this material, scientists have come up with better recipes for how to make planets, comets and asteroids. They were expecting to see water ice and silicates, but they were surprised to see materials like clay and carbonates (ingredient in seashells), since it was believed they required liquid water to form.