Hype, reality, and Mars

Mars, as depicted in "Starry Nights" software about midnight on August 27, 2003, from Westport, MA. (Large photo on right is superimposed over star map which shows Mars as the bright "star" just to left of center.)

Dom writes:

Here are the headlines of an email I received today:

MARK AUGUST 27th ON YOUR CALENDAR

MARS WILL APPEAR AS BIG AS THE MOON!

FIRST TIME IN AT LEAST 5,000 YEARS!

Never again in your lifetime will the Red Planet be
so spectacular!

Is it a hoax or is it true? (No doubt some poetic licence is being
exercised re Mars being as big as the moon.)

If true, will Driftway Observatory be taking photos and blogging them?

Is Driftway Observatory's chief astronomer excited?

Ah - I've been meaning to write about this. "It's true, I might," and "not very" are the short answers to the questions. (The "moon" headline is really misleading, but I'll deal with that later.)

It is not a hoax - it is true to the letter of the scientific law - but frankly, we get to see Mars almost this good every 15 or 17 years, and pretty good every two years. So for this and other reasons I fear this is being overdone. Yes, this is probably the best opportunity of my lifetime (and yours) to view Mars. Yes, I encourage you to take advantage of it. But don't expect too much. I have found Mars always to be a disappointing object in my telescope. So I see it as the best opportunity of my lifetime to do something I expect to find disappointing ;-)

Like all astronomical observing, though, it depends on what expectations you bring to the telescope. Photos from spacecraft over the past three decades have given us far better views of Mars and other planets than what we would see in the best of Earth-bound telescopes. So the first caution is do not expect to see what you see in the photos.

That said, even the folks I trust the most on such subjects - Sky and Telescope - are waxing poetic, but with the same cautions I would give. Their article begins:

It's not enough to describe the 2003 apparition of Mars as unique. In late August, as if beckoning us to touch its enchanting, exotic shores, the red planet will reach magnitude –2.9 and will dominate the southern sky with its fiery coloration. Finally, on the night of August 26–27, Mars will be closer to Earth — if by only a little — than at any time in some 60,000 years (see "A Mars Record For The Ages").

When the broadcast entertainment industry awakens to this remarkable fact, the airwaves will be filled with replays of classic movies like The War of the Worlds and the 1938 radio hoax staged by Orson Welles. A rush not seen since the 1986 visit of Halley's Comet could overwhelm the telescope market. The event is almost a certainty to fire the public's imagination as few other astronomical events can.

But amateur astronomers already know that Mars is always a telescopic challenge. Despite its remarkable proximity this time, Mars's features will be more elusive than its next-door-neighbor status would suggest. Faced with a public that's clamoring for views at summer star parties, inexperienced observers will have a hard time impressing their audience. For Mars, an angular extent of 25.1" is as good as it gets, but that's barely more than half the apparent diameter of Jupiter.

I expect the news media to get downright silly about this.

How difficult is Mars to observe? Keep in mind that just a century ago - with a telescope far better than most amateurs posses today - Astronomer Percival Lowell thought he detected canals on Mars and was convinced that Mars was an arid planet whose intelligent inhabitants were clinging to life through their technological skills. Other expert observers saw these "canals" as well, though they differed in their interpretation of them. When I have viewed Mars in the past I have detected some hints of the ice caps amid a general reddish glow. Nothing else.

Now I hasten to add that I am not an experienced planetary observer. But I always see three or four bands on Jupiter with a casual glance and I have occasionally detected several more bands and the "great red spot." But in the process I have also learned that planetary observing is a skill and other amateurs are far, far more skillful than I and genuinely see much more. It doesn't simply depend upon great vision. It requires patience and excellent "seeing" conditions. That last means the atmosphere should be still and such stillness - even on the best of nights - can vary from second to second. So one moment you see something and the next you don't and frankly, you wonder a lot if your eyes are playing tricks on you. Having experienced this, I forgive Percival his canals ;-)

As planets go, Saturn is the most impressive sight in a small telescope because its rings give it a three-dimensional effect. Next is Jupiter with its four prominent, Galilean moons that change position by the hour. But Mars presents special problems and a surface that is seldom very interesting - unless you happen to see canals and imagine little green folks running around, recylcing their perspiration as drinking water.

The orbit of Mars is elliptical and most of the time there's a huge gap between us and Mars. We close that gap every two years. But being close can mean anything from 55 million kilometers to 100 million kilometers. That's a tremendous variation. Every 15 years or 17 years - sometimes 15, sometimes 17 - we are in the 55 million kilometers ball park.

The important point is how big does it appear to be in our telescope at such times? The answer this year is 25.1 seconds in diameter. Don't worry if the term "seconds" doesn't make sense to you - just look at the comparison numbers:

August 1971 - 24.9"
September 1988 - 23.8"
June 2001 - 20.8"
August 2003 - 25.1

At other times when we are "close" Mars can be as small as 14". On the other hand, ideal times to see Jupiter come each year and during this decade Jupiter's disk will appear to us to vary from 45" to 50" in diameter. (There are "favorable" approaches when it can appear smaller, but never as small as Mars appears at its largest. )

Mars will be very impressive to the naked eye, but for us in Massachusetts it will also appear quite low in our southern sky. When it is closest the highest it will get above our horizon is about 28 degrees. (Hold out your fist at arms length, vertically, and it covers about 10 degrees.) This means we'll be looking through quite a bit of atmosphere and that also makes the view poor. (The higher something is in the sky the less atmosphere you have to look through and thus the better the view. Air's very handy when you're breathing, a pain when you're trying to look through several miles of it.) To put that in perspective, the next time Jupiter will be at its best is in early March, 2004, when at midnight it will be almost 55 degrees above our southern horizon. This altitude factor, however, varies significantly depending on where on our world you happen to be sitting.

But all of this fuels my skepticism. I'm bracing for a media onslaught I expect will irritate me and frustrate folks who read only the headlines - or get their news from that special class of idiots who live in our television sets. (Sorry - those folks are getting on my nerves lately.)

MARS WILL APPEAR AS BIG AS THE MOON!

That's the kind of headline I expect. True - if you know that they mean that Mars in a telescope , will appear to be as large as the moon appears to our naked eye. The deception is greater, however, because the moon seems to be so much larger because it is so bright. Truth is, the moon and the sun are both quite small to our view - about half a degree in diameter. If you are familiar with the "pointer" stars in the cup of the Big Dipper, then think of this: You can fit 11 full moons between those two stars! Hold your little finger at arms length and you can cover the full moon. So it is not nearly as large as it's brightness makes it appear to be.

The headline writer - perhaps out of ignorance - is toying with us. We have an impression of the moon as huge, especially if we remember it from when it is full and near the horizon. Mars, even in a telescope, won't come close to competing with this impression. But it will be - is already - the dominant feature in our southern night sky, out-shining all stars in the region by far.

Dom asks will I take photos? We seem to be permanently fogged in these days - absolutely horrible weather. Neither sun nor rain - just air that is so saturated with water that you feel like you need to wear a snorkel just to walk to the mail box. I might - but as I think about it, I might not be able to see Mars from the observatory. It may be too low in my southern sky. Trees will probably hide it. So I think I'll leave the picture taking to others more skilled.

Am I excited? No. I want to see it. I think visual observing is a tremendous experience and worth some serious meditation about what you are actually seeing. We can be much too glib about all this. But there are many astronomical events I'd rather witness, such as a really good meteor shower, an eclipse of the sun, a nearby super nova - or for that matter, Saturn just about any time.

But I'm more concerned that this will be oversold and genuine interest in astronomy will be set back by the building of false expectations. This will sell a lot of small telescopes, a lot of folks will go out to look, and I fear many will be disappointed.

But as I said, lower your expectations, ignore the media hype, and by all means enjoy this close encounter of the Martian kind. It is a rare event, even if they're shaving it a bit thin whenthey hype it as such.

Posted by Greg Stone at August 7, 2003 12:39 PM