One of the most mysterious places in the Solar System is right underneath your feet: the interior workings of the Earth. Since it's impossible to drill down more than a few km under the surface of the Earth, scientists have study how sound waves from earthquakes travel throughout the planet and get reflected as they bump into things. These sound waves have always acted differently than predicted in simulation. Scientists now think that iron, crushed under tremendous pressure, can significantly alter the speed and direction of these sound waves.

Engineers are still working to troubleshoot a malfunctioning fuel gauge on the space shuttle Discovery's external tank, but NASA has pinned down a launch date anyway. If all goes well, Discovery is expected to lift off on Tuesday, July 26 at 1439 UTC (10:39 am EDT). Even if the fuel sensor fails again, managers will go ahead with the launch, as they don't believe there's a risk to the shuttle - there are 3 additional sensors that perform the same task.

Supernovae are powerful stellar explosions that flare up brightly and then slowly fade away. But not always. One supernova, that exploded in 1979, is blazing as brightly in X-rays as it did when it was first discovered. The discovery was made using the ESA's XMM-Newton space telescope. Scientists speculate that a powerful solar wind is smashing into previously ejected material, heated it up until it glows brightly. This is like a powerful light illuminating the whole area, and allowing the astronomers to study the whole area for years and see how it changes over time.

Astronomers have used the massive Gemini and W.M. Keck observatories to discover a Sun-like star with one of the warmest, dustiest environments ever seen. The disk around star BD +20 307 is warmer than most other planetary disks because there have probably been recent collisions between planets. In fact the heat is so high, the researchers think a collision recently occurred that matches a cataclysmic event in the Earth's past when a Mars-sized object smashed into our planet, and spun off material that became the Moon.

Since scientists announced the discovery of methane in the atmosphere of Mars last year, there has been a controversy about whether this is an indication of life on the planet or not. Methane should only last a few hundred years in the Martian atmosphere before it breaks apart, so some source is continually producing it. On Earth, the main source of methane is from life; mainly microbes. But could there be some other natural geological process on Mars keeping this gas in the atmosphere?

NASA is targeting July 26, 2005 as the earliest date for the space shuttle Discovery to return to flight. Engineers are still working through a troubleshooting plan to get to the bottom of a problem with a liquid hydrogen low-level sensor circuit that forced managers to abort the launch last week. Discovery's launch window lasts until July 31, and then opens up again in September.

Astronomers from MIT and Williams College have teamed up to capture an event seen only once, 25 years ago. On the night of July 10/11, Pluto's moon Charon briefly passed in front of a distant star - this is called an occultation. By studying how the light from this star dimmed and then brightened again, the astronomers will be able to determine if Charon has an atmosphere. Charon is small, so it doesn't have much gravity to hold an atmosphere, but it's so cold that some gasses could be held in place.

Observations with the Chandra X-Ray Observatory have given astronomers some clues about what causes millisecond pulsars - extremely dense stars which can spin many times a second. Several of these pulsars were discovered in a stellar cluster called 47 Tucanae, where the stars are less than .1 light years apart. Astronomers think these pulsars started as regular neutron stars, but tightly joined with stellar companions they picked up in the cluster. Eventually they get so close they start drawing material off the companion, which causes them to speed up.

On December 27, 2004, a neutron star flared up so brightly, it temporarily blinded all the X-ray satellites in space for an instant, and lit up the Earth's upper atmosphere. This tremendous blast of energy was from a giant flare created by the neutron star's twisting magnetic field. Objects like this are called magnetars, and they produce magnetic fields trillions of time more powerful than those here on Earth. These fields are so strong they can actually buckle the surface of the neutron star causing these powerful star quakes.

Astronomers from the Harvard-Smithsonian Center for Astrophysics have found a dusty disk around a star which is 25 million years old. Planetary disks like this have been seen before, but never around a star which is so old; it's possible it'll never form planets. Most planetary disks make the transition within just a few million years, and the previous record was 10 million years. The disk still has a lot of gas in it, so researchers think it's still possible that it could form gas giants.

Scientists can tell us what our climate on Earth was like in past by examining ice cores taken from glaciers. Tiny bubbles of air are trapped in the ice and maintain a historical record of ancient atmospheres. The effects of life make their mark in these ice samples as well. What if you examined the icecaps on Mars, or the layers of ice on Europa? NASA is considering a proposal for a small spacecraft that would land on Mars or Europa and melt its way throught the ice, collecting data as it descended, searching for clues about the presence of life.