Opportunity took a last look back at the 22-metre "Eagle Crater" that it called home for two months while providing incredible evidence of Mars' watery past. This panoramic photo shows just how flat the Meridiani Planum region is. The area is surrounded by windblown sand, which indicates that wind is the primary geologic process going on here. There are two interesting depressions in the ground that Opportunity will examine before heading off to another crater.

The European Space Agency's SMART-1 spacecraft completed its 250th orbit this week on its long, slow journey to the Moon. The spacecraft's solar-powered ion engine is being turned on for 1.5 hours at the low point of each orbit. This slowly (and efficiently) raises the spacecraft in larger and larger orbits until it finally gets caught by the Moon's gravity - then it will decrease its orbit until it's going around the Moon. This whole journey will take 16 months, with SMART-1 arriving in lunar orbit in March 2005.

NASA has scheduled March 27 for the next flight for the experimental X-43A research vehicle. The unpiloted 4-metre prototype will be carried to supersonic speeds on the front of a Pegasus rocket. It will then fly under its own power using an air-breathing scramjet engine to reach Mach 7. A scramjet scoops oxygen from the air as it flies, and uses this to combust its fuel. This is the second test of a X-43A prototype; the first was destroyed because of a problem with the Pegasus booster.

NASA announced today that Opportunity has found evidence that the rocks around it were built up at the bottom of an ancient Martian salty ocean. The rover has found evidence of cross-bedding, where inclined layers of rocks are formed through sedimentation. Scientists aren't sure how long ago the sediments were created, so they're planning to send Opportunity to another outcropping of rock to make more observations. These kinds of rock formations are ideal for finding fossil evidence of past life; unfortunately, Opportunity's instruments aren't sensitive enough to see fossils if they're there.

Dark matter is a mystery. Astronomers know it's there because they can measure the effect of its gravity on stars and galaxies, but they can't see it. One theory about the nature of dark matter is that it's composed of theoretical subatomic particles called Weakly Interacting Massive Particles (WIMPS). A team from Italy believed they detected these WIMPs back in 1998, but other scientists were skeptical. A researcher from the University of Utah has proposed that the Italians search for different streams of particles coming from different galaxies to validate their original experiment.

Astronomers have measured the light from a supernova, and believe that it was inside a very unusual star system when it exploded. The team used the European Southern Observatory's Very Large Telescope in Chile to analyze the light from supernova 2002ic, and determined that it was inside a flat, dense, clumpy disk of dust and gas that was previously blown out by a companion star. It seems similar to objects known as protoplanetary nebulae, which are found in our own Milky Way.

NASA's Opportunity has crawled out of the crater it landed in, and turned back to survey its old home. Getting out of the hole wasn't as easy as NASA originally thought it was going to be. The Opportunity made an attempt to drive out of the crater, but the slope was so steep it slipped back down. Operators finally found a route that was gentle enough for the rover to get out and onto the plains above. The 22-metre crater has been named "Eagle Crater"

Amateur astronomer Jay McNeil made a lucky discovery last month when he noticed a new smudge of dust in the constellation of Orion using his 3-inch telescope - it turned out McNeil had discovered a nebula surrounding a newborn star that was illuminated when the star flared up. After his discovery, observatories around the world turned their larger instruments on "McNeil's Nebula" to get a better understanding of what's happening in this stellar nursery. This latest image was taken by the 8-metre Gemini observatory in Hawaii.

NASA's Cassini spacecraft took this latest picture of Saturn this week when it was 59.9 million kilometres away. The photo was taken using Cassini's BL1 broadband spectral filter. A full colour composite picture is built up by adding together images taken in the blue, red and green spectrums. Three of Saturn's moons can be seen in the image: Enceladus, Mimas, and Rhea. Cassini will be releasing new images once a week until it reaches Saturn in July 2004.

When they look at Io, one of Jupiter's moons, researchers think they could be seeing that the Earth might have looked like in its early history, before the development of plate tectonics - 200 to 500 million years after the planet formed. Volcanically active Io is being constantly pulled by Jupiter and another of its moons, Europa, so plate tectonics have never taken hold. On Earth, volcanic hotspots form at the edges of plates, but on Io they are circular.

Beginning tonight, and lasting for about two weeks, all five planets visible to the unaided eye will be in the sky - a nighttime planetary grouping that won't be back again until 2036. To get the best view, head somewhere with a clear view to the Western horizon (you should still be able to see all the planets, even from a light-polluted urban environment). Mercury is just above the horizon (near the Moon tonight), Venus is the bright star high in the Western sky, Mars is a reddish star just above Venus, Saturn is almost directly overhead, and Jupiter is the brightest object in the Eastern sky.

A Boeing Delta II rocket launched the 50th Global Positioning System (GPS) satellite on Saturday. The rocket lifted off from Cape Canaveral at 1753 UTC (12:53 pm EST), after a brief delay because of a problem with the upper stage's nitrogen system. The Lockheed Martin-built satellite joins 27 others already in orbit, to provide navigational information to both civilians and the military.

Billionaire Paul Allen has committed $13.5 million to support the construction of the first and second phases of the Allen Telescope Array. Construction of the array is now underway at the Hat Creek Observatory, 466 km northeast of San Francisco; the first phase will include the development of 32 6.1-metre radio telescopes. The second phase will see an additional 174 built. Eventually there will be a total of 350 identical dishes built. Once the first 32 dishes are completed, the array can begin scientific operations.

While watching the night sky with its panoramic camera, NASA's Spirit rover saw something surprising - a streak of light that was probably the brightest object in the sky. But what was it? It could have been a meteorite, or an old, dead spacecraft that orbited overhead. Based on the direction of the trail, the only spacecraft in that orbit, moving at that velocity would be Viking 2.

Scientists think they have an explanation for the "dust bowl" droughts of the 1930s, which helped to cause the Great Depression in the United States. Using a climate model called NASA's Seasonal-to-Interannual Prediction Project (NSIPP), researchers were able to see how unusual temperatures in both the Pacific and Atlantic Oceans could divert the path of the jet stream, which normally dumps rain in the US Great Plains. This lack of water created a feedback loop which reinforced the drought, which is why it lasted for nearly a decade.

NASA's Opportunity rover has determined that the small mineral spherules, which scientists have been calling "blueberries", contain hematite. This furthers the theory that the region was once drenched with liquid water. On Earth, hematite crystals with the same size as the spherules usually form in a wet environment. Doing a chemical analysis on the spherules was difficult because they're too small for any of Opportunity's instruments. The rover had to find a spot which was covered with spherules to analyze.

Make sure you keep your eyes turned to the night sky for the next couple of weeks - you'll be able to see all five planets visible to the unaided eye. Mercury is down near the Western horizon, and sets quickly after sunset. Venus is also the West, and the brightest object in the sky after the Moon. Mars is a small reddish star above Venus. Saturn is nearly directly overhead, and Jupiter is the next brightest object, low in the Eastern horizon after sunset. You won't need a telescope to see them all, but if you can get your hands on one, you're in for an even better view.

NASA and the US Department of Energy announced this week that they will be working together to develop a nuclear reactor system for space exploration. One goal for this partnership will be to develop the Jupiter Icy Moons Orbiter (JIMO) mission, which will visit and examine Jupiter's three icy moons. The reactor will provide the electricity for a high-powered ion engine, which will allow JIMO to get into orbit around each moon and then out again.