Water is a precious commodity for earthlings; we need rain although not necessarily when it causes a flood. Among the planets in our solar system, water in liquid form is only known to be abundant on the Earth where temperatures are just right for it to exist and life as we know it to survive.
Spacecraft imagery in recent years, however, has pointed to the likelihood of an ocean beneath the frozen surface of Jupiter’s moon, Europa.
Mars apparently overflowed with liquid water in its distant past, as is abundantly evident from exploration by the amazing robotic craft “Spirit” and “Opportunity” on the Martian landscape since 2004 (Spirit finally quit in 2010 but Opportunity is still hard at work). Close-up examination of the rocks and soil by these craft have confirmed the past presence of flowing water that carved now-dry river channels, canyons and lakes, known to exist for decades since space craft have been flying past or around Mars.
The signature of water is revealed among the stars in the astronomer’s spectrometers. Chemical elements such as hydrogen and oxygen as well as carbon, helium and all the others – and their compounds including water (two parts hydrogen and one part oxygen, or H2O) are revealed as lines sliced through the colorful spectrum from star light. A spectroscope, using a glass prism or extremely fine-lined grating, breaks up the white light entering the telescope, into its component rainbow colors. The chemical elements absorb a narrow frequency of the light, removing it from the band of colors and allowing the astronomer to identify what the source of light (such as a star) is made up of.
Most of the solar system is quite dry – in fact, drier than anywhere on Earth’s surface even the deserts. If there is water, it is usually solid ice, on planets or their moons. The Earth’s moon is bone dry, although there is still suspicion that there may lie masses of ice in the dark craters and crevices of the polar regions where sunlight never reaches. That ice would have come from bombardment of comets, which are contain a great deal of water ice. Space scientists remain hopeful that such ice deposits are there and can be tapped by future moon colonies.
There may not be rain storms of water elsewhere in the Solar System, but on Venus sulfuric acid is expected to rain down, and on Titan, the largest moon of Saturn, it rains liquid methane.
Titan is known to have a crust of rock-hard water ice. Cassini spacecraft studies, from its orbit around Saturn, have found evidence of a liquid methane lake in Titan’s tropics and hydrocarbon lakes at the poles.
A quick look at the known composition of the atmospheres of each planet shows the Earth the place to be unless you want to live in a spacesuit.
Practically airless, Mercury has traces of hydrogen and helium. Venus, nearly the Earth’s size, is perpetually cloudy and its air is 96 percent carbon dioxide, 3 percent nitrogen and only 0.1 percent water vapor. Earth has 78 percent nitrogen, 21 percent oxygen and 1 percent argon. Mars has 95 percent carbon dioxide, 3 percent nitrogen and 1.6 percent argon. Hydrogen is the main element in the completely cloudy atmospheres of the giant planets, Jupiter, Saturn, Uranus and Neptune. The air of Pluto, if any, may include methane and nitrogen.
We can indeed be thankful for our friendly abode we call Earth.
If our own atmosphere clears enough, this week enjoy the view of the planets from your own backyard. Breath in the fresh air (assuming the neighbor isn’t burning plastic again). Soak up the water so precious to life (by the bucketful if you don’t have a sump pump). Be glad for the temperate climate of Earth’s orbit about the sun where mankind never fries or literally freezes solid as we would on other worlds (without your space suit)- and remember that when the fuel bill comes in the winter or you reach for that air conditioner or fan in the summer!
About 45 minutes after sunset, look low in the west-northwest for planet Mercury. The crescent moon wil be to the upper left this weekend, heading toward first quarter on June 26. Look to the south for the bright planet Saturn right above the star Spica, which is about the same magnitude. Reddish Mars is to the right in the southwest. Just before dawn look east-northeast for Venus low in the sky and Jupiter to the upper right. The Plieades star cluster gleams nearby Jupiter. Binoculars will help you see them through the morning glow.
Some handy resources on the Internet include www.nineplanets.org, www.skyandtelescope.com and www.astronomy.com. Also, patronize your local public library and ask for their astronomy books!
Notes are welcome at firstname.lastname@example.org; please mention where you read this column.
Keeping looking up!