Mars is bright now

Central Oregon viewing of red planet is great tonight

The moon will rise later throughout the week, providing longer viewing opportunities for observing Mars without interfering light. Look to the east. To the unaided eye, Mars appears as a tiny orange dot at a distance of 0.618 astronomic units (AU), or about 57 million miles. Arcturus, a star, is nearby and left of Mars and is often mistaken for Mars due to its similar color. Arcturus is in fact a huge red giant star far outside the solar system, 36.7 light-years away.

Mars, named for the Roman god of war, is the fourth planet from the sun. The farther out a planet orbits, the slower its speed is, and its orbital path is longer. While Earth’s year is 365.25 days, the Martian year is 686.98 days. Each solar day on Mars (“sol”) is 24 hours, 39 minutes and 35.244 seconds, only slightly longer than an Earth day. Surface gravity is weak, about 38 percent of Earth’s. The atmosphere is extremely thin, only 0.6 percent of Earth’s, and 95 percent of that is carbon dioxide. Mars’ two known moons, Phobos and Deimos, were discovered by American astronomer Asaph Hall over the course of a single week back in 1877.

Early astronomers, believing in an Earth-centered system, were confounded by Mars’ apparent retrograde motion; Mars seems to back up in a looping movement and then go forward again. This illusion is created as Earth in its orbit approaches and overtakes Mars in its more distant orbit. From our perspective, Mars appears to back up in relation to background stars and then move forward again. Geocentric models were hard-pressed to create a credible explanation and never really did so. The heliocentric (sun-centered) system solved the problematic observance created by observational perspective.

Various probes have confirmed that Mars does have water as ice locked in polar caps and in shallow subsurface locations at more temperate latitudes. The Martian landscape suggests that great quantities of liquid surface water may have been present in the past. If so, where has it gone? An answer might uncover important information concerning planetary evolution here on Earth. Although Mars has been extensively studied for signs of life, no definitive evidence has, as yet, been found.

— Kent Fairfield is a volunteer with Pine Mountain Observatory and a lifelong amateur astronomer. He can be reached at kent.fairfield@gmail.com. Other PMO volunteers also contributed to this article.