It's building since early spring, culminating at the end of this month – the great 2018 Mars Show.
Earth and Mars have their next approach in 15 years. In 2003, Mars and Earth were only 34,646,418 miles apart, and although that's a pretty long distance, it was what the two planets were closest to in almost 60,000 years. In the early hours of July 31st, Mars will be only 35785.537 miles from Earth, less than 1.2 million miles down from 2003.
For all practical purposes, Mars will be so big and be bright as it was then. With the exception of Venus, which sets in the western sky in the early evening, until the beginning of September Mars will be the brightest star object in the whole sky. If you ever needed an excuse to buy a telescope, that's it! Mars will not be that close again until 2035.
To add to the series this week, the full moon will be in heavenly embrace with Mars as it rises Thursday and Friday evenings. On Thursday night, the Moon will be just above and to the right of Mars, and Friday night will be on the top left of our Mars neighbor. Do not miss this great conjunction!
Mars and the earth are this week what astronomers call "opposition". As you can see in the diagram, this means that Mars and Earth are at a minimum. It also provides Mars all night and rises at sunset and setting at sunrise. The Earth needs 365.25 days to complete the orbit around the Sun while it lasts 587 days. As a result, Mars and Earth come into opposition about every two years. The earth is roughly in line between Mars and the sun.
Not all opposites are the same. Some bring Mars and Earth closer together than others. This is because the orbits of the two planets are ellipses rather than perfect circles. The orbit of Mars is slightly more elliptical or oval than Earth's orbit, as you can see in the diagram. For explanatory purposes, however, the ellipse is a bit exaggerated.
Due to their elliptical orbits, both Mars and Earth have a minimum and maximum distance to the Sun. In the case of Earth, the difference between our minimum and maximum distance from the Sun is not nearly as large as in the case of Mars. During the Mars-Earth opposition of 2018, the Earth is near its distance from the Sun and Mars is very close to its minimum distance, making Mars and Earth very close together, similar to 2003.
This is usually a wonderful time to study Mars, even with a small to medium telescope. Mars is the only planet in our solar system where you can actually see the surface. On other planets like Jupiter, Saturn and Venus only cloud tops are visible. However, I do not want to exaggerate what you will see on Mars. It's still only a 4000-mile-wide planet, nearly 36 million miles away. Even at higher magnification, it will not fill the field of your telescope eyepiece.
However, and this is a big "however", there is bad news with this year's opposition. There is a global dust storm that darkens the red planet. At the moment it looks like it will continue until August and maybe even until September. The storm is similar to that which occurred in 2001, when Mars and Earth were also close to each other. There is a possibility that the current forecast for the storm is not complete and we could get a break. Let's hope so! Otherwise you can see on Mars through a telescope of any size a large orange disc, and that's it.
If the storm subsides and you can see Mars, here's some advice. To get your best outlook on Mars, stay up late every evening as you try to catch a glimpse of it in mid-August. Even without a cloud of dust, when you aim your riflescope at Mars when it first rises, you get a really blurry, distorted view, because the Earth has a thicker layer of blurry atmosphere near the horizon. It's best to wait until after midnight, and even better if you wait until one in the morning when the planet reaches its maximum altitude in the sky above the southern horizon.
Unfortunately, with Mars set against the backdrop of stars and our latitude in Minnesota and West Wisconsin, even at its maximum altitude, it will be less than a third of the way from the horizon to the zenith peak. At this low altitude there will still be some blurring effects. High humidity will also blur the view. Ideally, to have a better view and to have Mars higher in the sky, travel to the south of the US or even further south where you generally have more transparent views.
It is still possible to get a nice view of Mars through a telescope around here – when the mire gets in the sky – especially from midnight to 2 o'clock in the morning. It is important to be patient, to be in a comfortable position while looking through the perimeter, and to have long uninterrupted views of Mars, at least five to ten minutes at a time. This gives your eye the ability to adjust to the level of light in the eyepiece and use less turbulent and more transparent openings in the atmosphere.
Depending on how well you can see, you should be able to see the south of Mars polar cap, which consists mainly of frozen carbon dioxide. If your telescope shows you a reverse image, as most do, the southern pole cap will be pointed at the upper extremity or disk of the planet. With larger telescopes, and even small to moderate, you can see dark spots on Mars. These are rocky fields, plains and huge ravines on the surface. There is even a huge dormant volcano called Olympus Mons. As Mars rotates about its axis every 24 1/2 hours, a little slower than our Earth, you'll see alternating patterns of dark spots from night to night and even over several hours.
Sky and Telescope Magazine has a great tool available on their website, skyandtelecope.com. It's called the Mars Profiler, and it lets you know which surface features are visible on Mars at all times on Earth. Just search on their website.
Here's another tip about using your telescope: Make sure your telescope and all the eyepieces you use sit outside for a good half to full hour to allow all the mirrors and glass to adjust to outside temperatures. It really makes a difference.