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DARK SKIES

The August night sky

óCharlie Christmann

    Mars!

This is the month. On August 27, Mars will be less than 34.65 million miles away from Earth, closer to our planet than itís been in nearly sixty thousand years. At 3:51 a.m. MDT on that day, the apparent disk diameter of Mars will be the absolute maximum possible. What does this mean? Mars will never be closer, bigger, or brighter, at least not in our lifetime, unless you plan to be around on August 28, 2287.

    A Southern Summer on Mars

Like Earth, Mars has seasons, but they average almost twice as long as ours, since Mars takes longer to go around the Sun. This year, the spring equinox in the Martian southern hemisphere occurred on May 5, and the summer solstice falls on September 29. The Martian South Pole has been tilted toward the Earth since the end of February and will continue to do so through the rest of 2003. This orientation gives us an excellent view of the south polar cap. The cap appeared at its largest a few months ago, and its subsequent shrinkage has made for interesting telescope viewing.

The wintertime polar clouds are in the process of dissipating. This ultimately will leave the entire south cap shining brilliantly and will allow us to watch the spring thaw. Scientists believe the polar caps are composed of a mixture of regular snow and ice as well as frozen carbon dioxide, commonly called dry ice.

    Canals of Mars

Astronomers Giovanni Schiaparelli and Percival Lowell reported observing canals on Mars in the late nineteenth and early twentieth centuries. Schiaparelli was the first to observe the strange markings on the surface in 1877 and termed them canali, which in Italian meant "channels." He was misinterpreted, though, and the lines became widely known as canals, a term which suggested that rather than a natural phenomenon, that they were constructed by intelligent beings. Later, Lowell took the matter one step further, expressing his belief that the canals had been constructed by an advanced race of beings who dug them with the intention of bringing fresh water down from the poles.

Today, we know the channels are unrelated dark spots which are put together as continuous features by the observerís eye and mind.

    Martian Storms

If you think New Mexico has terrible dust storms, try Mars. Yellow dust storms tend to begin every Martian year soon after the summer solstice in the southern hemisphere of Mars. The dust storm season this year should start sometime in early or mid-October, though this is far from certain.

A dust storm typically appears quite suddenly as a bright, albeit small, yellow cloud, which over a span of days and weeks may ultimately obscure all of Mars for many months at a time, giving the planet the appearance of a blank orange disk.

    A Special Planetary Meeting

The relationship in space between Earth and Mars is never exactly repeated. Each planet orbits the Sun on its own elliptical path and those paths actually rotate through space over thousands of years. The result, in late August, will be a close encounter that hasn't occurred for seventy-three thousand years, according to a calculation made by Jean Meeus in November. Interestingly, even closer passes are predicted in the future.

The main reason for the alteration in distance between the two planets is the fact that Earth takes a path closer to the Sun. Physics dictates that inner planets must zip around more quickly than outer planets. Earth requires 365 days to go around the Sun once. Mars needs 687 Earth days to complete its orbit.

Right now, Earth is catching up with Mars every day. When we pass, Earth and Mars will be on the same side of the Sun, as seen from above. The Sun, Earth, and Mars will be lined up in a row. This happens about every twenty-six months. When this configuration occurs, astronomers say Mars is at opposition.

The distances between Earth and Mars during these oppositions vary wildly. The last opposition, in 2001, involved a separation of more than forty-one million miles. In 1995, the distance between the two worlds was nearly double what it will be later this year.

Both the Earth and Mars are in elliptical orbits around the Sun. Earth's distance from the Sun varies from its average by nearly two percent, and the distance of Mars varies from its average by more than nine percent nearer and farther. These nearest and farthest points slowly change their positions in space over thousands of years. They are presently evolving toward alignment. When they do get nearly aligned and when Mars and Earth pass near the key points at the same time, then a truly close approach occurs.

    Perseid Meteor Shower 2003

The Perseid meteor shower will be appearing in 2003 from July 17 to August 24 and will peak August 12 through 14. Over the last couple of years, the Perseids have given us a great show. This yearís event will peak during a full moon, which will interfere with our viewing of the event. Expect about eighty meteors per hour.

    Where are the Planets and the Moon?

  • Mercury will be visible in the early evening twilight.
  • Venus is below the horizon and not visible.
  • Mars is visible all night.
  • Jupiter slides into the setting sun in August and will no longer be visible.
  • Saturn will rise around 3:00 a.m.
  • The moon is full on August 12.
  • The new moon is on August 27.

 

 

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