BACKGROUND: For years, the Hubble Space Telescope has given scientists spectacular photographs of the farthest reaches of space, but recently the telescope turned its attention a bit closer to home, taking images of the moon. These images -- the first taken with ultraviolet light -- reveal new information about the composition of the moon, with implications for future lunar exploration.
HOW HUBBLE WORKS: Hubble has a long tube that is open at one end, with mirrors to gather and focus light to its "eyes" -- various instruments that enable it to detect different types of light, such as ultraviolet and infrared. Light enters the telescope through the opening and bounces off a primary mirror to a secondary mirror, which reflects the light through a hole in the center of the primary mirror to a focal point behind the primary mirror.
Smaller mirrors distribute the light to the various scientific instruments, which analyze the different wavelengths. Each instrument uses the same kind of array of diodes that are used in digital cameras to capture light. The captured light is stored in on-board computers and relayed to Earth as digital signals, and this data is then transformed into images.
WHAT WE CAN LEARN: Astronomers can glean a lot of useful scientific information from these images. The colors, or spectrum, of light coming from a celestial object form a chemical fingerprint of that object, indicating which elements are present, while the intensity of each color tells us how much of that element is present. The spectrum can also tell astronomers how fast a celestial object is moving away or towards us through an effect called the Doppler shift. Light emitted by a moving object is perceived to increase in frequency (a blue shift) if it is moving toward the observer; if the object is moving away from us, it will be shifted toward the red end of the spectrum.
NEW INSIGHTS: Thanks to Hubble's high resolution and sensitivity to ultraviolet light, astronomers are able to search for minerals in the lunar crust that may be critical for establishing a sustained human presence on the moon. These include titanium and iron oxides, both of which are sources of oxygen. Since the moon lacks a breathable atmosphere (as well as water), the presence of such minerals is critical. This new data, along with other measurements will help NASA scientists identify the most promising sites for future robotic and human missions.