Now is good time to view red planet


By Tom Burns - Stargazing



During the next few weeks, we get a rare opportunity to examine the surface of Mars in amateur telescopes.

Mars, nicely positioned between the horns of Taurus, the Bull, is high in the eastern sky by 9 p.m. It will reach its closest point to Earth on Dec. 1 and be in a more-or-less direct line with the sun and Earth, a phenomenon called opposition, on Dec. 8.

Oppositions happen only every 26 months, so right now is an excellent time to dust off your telescope and look at the red planet.

However, not all oppositions produce good images of Mars in a telescope. Every 15-17 years, Mars and Earth get particularly close — as close as 34 million miles.

This year’s opposition is not one of them, unfortunately. For that, you’ll have to wait until 2033. However, Mars’ current distance from Earth, about 50 million miles, is nothing to sneeze at.

The last close opposition in 2018 passed without an extraordinary amount of hoopla.

In August 2003, we experienced a truly magnificent close approach. The hoopla reached gigantic proportions. “The best Martian apparition in 60,000 years,” screamed the NASA press release.

Internet rumors suggested that Mars would be “as big as the full moon,” which was, of course, ridiculous. Mars is only twice the diameter of the moon, and the moon is only a quarter of a million miles away.

In 2003, the astronomical community tried to lower expectations but to no avail. My frank appraisal of the views seemed at odds with the media hype.

Most people see a red dot with a tiny white polar cap or two occasionally shimmering through our mostly turbulent atmosphere. A few greenish markings might be visible on the planet’s surface.

The simple fact is that Mars never fails to disappoint. You can maximize your experience by choosing the time you observe it.

Just after dark, Mars will just be rising in the east. At that point, it won’t be very far above the turbulent atmosphere close to the horizon. The image will shimmy and shake most of the time. You’ll have to stare at it for a minute or two and hope that the atmosphere settles down for a few seconds of “good seeing,” as we astronerds like to say.

Start looking around 9 p.m. You can minimize the effects of atmospheric turbulence by observing Mars when it is straight south and at its highest point in the sky, about 75 degrees above the horizon at 1 a.m.

By the second week in December, “Old Red” will have receded a bit, but it will still be worth a look. Start observing in the southeast at 8 p.m. The best views will be between midnight and 1 a.m. when Mars is again high in the south.

In a telescope, Mars looks a lot redder than it does to the unaided eye, courtesy of the Martian soil seasoned liberally with iron oxide, also known as rust.

Of course, you can’t predict the effects of Martian weather. Mars’ atmosphere is barely there — an exceedingly thin blanket of carbon dioxide. Any oxygen that might have helped to thicken the atmosphere a little is tied up in the soil as rust or has spun off into space.

But the Martian atmosphere is subject to powerful winds. Without warning, a planet-wide yellow dust storm can obscure the view for weeks. During a dust storm, you can forget about seeing surface features like its mysterious green markings.

If the Martian atmosphere is quiet, hope that our Earthly air isn’t moving around: A turbulent atmosphere above your observing location also will turn Mars into a fuzzy blob. If the image of Mars is sharp at low magnification, keep increasing the power until you begin to lose surface detail.

First, revel in the planet’s redness. Any color at all is a welcome change from the primarily monochromatic sky.

The white spots on the top and the bottom of Mars are its southern and northern polar caps, which will look pretty small in a telescope. The polar caps consist of layers of water ice and frozen carbon dioxide, also known as dry ice. Mars is a frigid planet.

Neither polar cap was present when I last observed Mars a week ago.

The green markings are the accumulated impression of various Martian features — mountains, valleys, and piles of rocky debris — all mixed together. These “features,” as astronerds call them, have exotic Latin names like Syrtis Major, Mare Acidalium, and Sinus Sabeus.

Mars’ orbital period is 24.6 hours, nearly the same as Earth’s. If you observe Mars at the same time every night, you’ll see one feature, like Syrtis Major, repeatedly. Try to observe the planet at various times of the night to see different features.

If you want to know what you’re looking at, you’ll find a map of all the Martian features at https://lovethenightsky.com/how-to-see-mars/.

If you spot a yellow patch that seems to obscure all or part of the green markings, you are seeing a giant Martian sandstorm.

As it turned out, Mars was the key to discovering our actual place in the universe.

Our forebears were confident that the planets traveled in perfect circles around the Earth. But planets such as Mars sometimes violate the “perfect circle” rule. At times, Mars appears to reverse direction and go into what astronomers call retrograde motion.

Ancient astronomers could not accurately predict the planet’s position. That unpredictability should have been the death blow to the Earth-centered model.

The Greek astronomer Ptolemy concocted a clever solution. As Mars orbits Earth, he hypothesized, it also orbits a point on its orbit.

Don’t let that throw you. It’s what happens on the teacups ride at an amusement park. In effect, Mars was making a “loop de loop” around Earth.

As our ability to measure the positions of the planets got better, astronomers had to add more orbits within orbits to predict the position of the planets mathematically. They had wheels within wheels within wheels and still couldn’t predict the planetary locations exactly.

Copernicus argued that the sun was at the center and the planets orbited it in perfect circles. Ironically, the Copernican system was no better at predicting the positions of the planets than the Ptolemaic, earth-centered model.

Galileo tried to use his telescope to prove the sun-centered hypothesis. His “proofs” — notably the phases of Venus and the moons of Jupiter — can be explained within the earth-centered model.

To prove the sun-centered hypothesis con irrefutably, somebody had to find a way to make the Copernican model accurately predict the positions of the planets.

That somebody was an obscure mathematician named Johannes Kepler. He arose from poverty. Abandoned by his father, he was forced to defend his mother against charges of witchcraft. His mentor and master, the great observational astronomer Tycho Brahe, treated him like a calculating machine.

But after his master died, Kepler kept Brahe’s extraordinarily accurate observations of the positions of the planets. With them, he could determine how and where the planets move. He started with Mars and its mysterious loop de loop. Years passed as Kepler ground away at the numbers.

In 1606 came a magnificent revelation. The orbits of the planets, Mars included, are stretched out — ellipses, not circles. When the planets are closer to the sun, they move faster.

As they move away from the sun, they slow down. Kepler had nailed it.

Retrograde motion can be explained as Earth, the third planet from the sun, catching up to Mars, the fourth planet, and passing it.

Kepler’s laws of planetary motion are mathematically precise. They tell us exactly where we can find Mars in the coming days.

That’s something to remember on the evening of Dec. 7, when the moon will pass in front of Mars.

Start by looking for the moon at about 9 p.m. EST. You’ll see the full moon in the eastern sky with Mars below it.

The moon will slowly move downward until Mars disappears behind Luna at 9:25. Mars will reappear at 9:58.

During every Martian opposition, I am reminded of the bizarre history of Marian speculation.

Early in the 20th century, noted Mars observer Percival Lowell saw the signs of a Martian civilization in the form of canals carved on the face of Mars. The canals simply don’t exist. To this day, nobody is sure what Lowell saw in his telescope.

Lowell’s canals were small potatoes compared with the later Martian meanderings of Russian astrophysicist Iosif Shklovsky.

In 1959, Shklovsky concluded that Phobos, one of the two small moons of Mars, must be very low in density. How could it weigh so little and still be rigid enough to hold together?

According to Shklovsky, Phobos must be an artificial satellite created by an advanced civilization on Mars some hundreds of millions of years ago. Twenty years later, well after the astronomical community’s diatribes had died down, a thoroughly chastened Shklovsky wrote that the whole thing had been a practical joke.

Yeah. Right.

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By Tom Burns

Stargazing

Tom Burns is the former director of the Perkins Observatory in Delaware.

Tom Burns is the former director of the Perkins Observatory in Delaware.