May Sky from Keeble Observatory
Mars Global Surveyor is sending back high-resolution images of the Martian surface. The spacecraft has now been placed in a circular orbit, completely circling the planet every two hours. This means that it passes over each pole 12 times a day, and should return map-quality images of the entire planet within a year or so.
It is currently summer in the Martian northern hemisphere. The polar cap is retreating in "balmy" temperatures which still remain below freezing. The ice doesn't melt, rather it sublimates - changing directly to vapor from its frozen state. In its next winter the process will reverse, and frost will build again, freezing directly out of the thin atmosphere. The cap is a mix of water ice, carbon dioxide "dry ice", and sandy layers deposited over the ages. Much of it is below the surface, insulated by even more dirt. As the surface layers retreat, we are able to see daily changes in dunes and wind-blown fines streaked across the remaining white icy surface. For a set of "eye-popping" images, check out their web site!
One possible fly in the ointment: the high gain antenna on Mars Global Surveyor stopped rotating properly on the 16th of April. The antenna is designed to swivel at the end of its deployment mast, keeping it pointed at Earth whenever the spacecraft is over the sunlit side of Mars. This allows about 10 hours daily of simultaneous mapping and data transmission. Data collected when the satellite is on the night side are stored on solid state recorders, and transmitted when the antenna is properly pointed. Mission controllers are evaluating ways to unstick it and recover the ability to map simultaneously with transmission. Reversion to a model of mapping, then swiveling the spacecraft to point the antenna, is possible, but would reduce the rate of data collection and transmission. We'll keep you informed.
Lunar phases for May: 3rd Quarter at 9:51 pm (EDT) on May 8th; New Moon on the 15th at 11:22 pm; 1st Quarter on the 22nd at 2:01 pm; Full Moon on the 30th at 9:55 am.
Venus continues its spectacular reign in the early evening skies, setting about two hours after sunset. It's hard to miss, since it's the brightest object in the west. Mars is visible all night, starting at twilight just off the southeast horizon. Mars will be at its closes distance to Earth on the 1st, a mere .578 astronomical units away (54 million miles, or 87 million kilometers). Jupiter returns to the early morning skies about mid-month, but Saturn is not observable from here until June (it was at conjunction on the 27th of April).The Eta Aquarid meteor shower will peak around the 6th, but the moon will make viewing difficult. A better chance occurs later in the month. The Omicron Cetids should peak on the 20th, and the moon sets early, leaving the after-midnight sky dark. Find a dark site away from city lights, and let your eyes adapt fully for best viewing.
An overhead view at about 9:00 pm finds the zenith almost empty of stars, but with several bright stars in nearly every direction at varying distances off the horizon. Castor and Pollux, in Gemini, are above Venus to the west. Shifting our view to the southwest we find Procyon, in Canis Minor, about the same altitude as Venus but not nearly as bright. Regulus and Denebola, in Leo, are higher and more southerly, with Regulus brighter and more to the west. Spica, in Virgo, is lower and to the southeast. Arcturus marks the eastern sky, in Bootes, with the bright stars of Ursa Major (the Big Dipper) inverted to the north. In the middle of a triangle, roughly formed by Procyon, Regulus, and Pollux, use your binoculars to find the Beehive Cluster, in Cancer. Sweeping your binoculars from Regulus toward Denebola, you may find the elliptical galaxy M105 about a third of the way between. Continuing a similar distance beyond Denebola will bring you to another elliptical, M87. To the north, just above the end star in the handle of the Dipper (Alkaid), you may be able to pick out M51, also known as the Whirlpool Galaxy. These are relatively faint objects, so you need a dark night, a dark site, and a bit of luck!