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Once in about every fifteen years a startling visitant makes his appearance upon our midnight skies,--a great red star
that ... mounting higher with the deepening night,
blazes forth against the dark background of space with a splendor that outshines Sirius and rivals the giant Jupiter
himself. -- from Mars by Percival Lowell (1895)
Apr. 23, 1999:
Go outside about 2 hours after sunset and look toward the East. That
brilliant red star you see just above the horizon is Mars, and
it's headed our way.
There's nothing to worry about. Mars won't come any closer to Earth
than about 54 million miles, but this week and next Mars will be
brighter and nearer to Earth than at any time since 1990. It's a
great opportunity for amateurs to see details on the red planet through
a small telescope or to simply view Mars with the naked eye.
Right: This NASA Hubble Space Telescope view of the planet Mars is the
clearest picture ever taken from Earth, surpassed only by close-up
shots sent back by visiting space probes. The picture was taken on
February 25, 1995, when Mars was at a distance of approximately 65
million miles from Earth. The Red Planet will be even closer to
Earth during the coming weeks. more information
On April 24, Mars reaches "opposition," which means that it
passes through a point in its orbit that is
directly opposite the sun as seen from Earth.
At opposition Mars rises near sunset and is visible
all night from most latitudes. Shining at magnitude
-1.6, it will appear to be one of the brightest stars in the sky on
Saturday night. In fact, it will be as bright as Sirius
and second only to Venus in brilliance.
"This is a great time to view Mars with the naked eye," says Dr. John
Horack, a NASA astronomer. "By mid- to late-June the planet will be a full magnitude
dimmer, but for the next few weeks it will be
spectacular."
To find Mars
simply go outside any night for the next couple
of weeks about an hour or two after sunset.
Reddish colored Mars should be easy to spot 20 to 25 degrees above the
horizon in the east-southeast. Later in the evening,
near midnight,
Mars can be seen due South about 45 degrees above the horizon from mid-latitude sites in
the northern hemisphere.
Left: On April 24, 1999 when Mars reaches
opposition, the planet can be found in the constellation Virgo about 15 degrees
East of the blue-white star Spica (magnitude 1.2). This image shows Mars and Virgo viewed
about 40 degrees above the southern horizon at 11:30 p.m. local time on April 24.
If the orbits of Mars and Earth were perfectly circular then the
two planets would be closest together on April 24 at the exact
moment of opposition.
But that's not the case. Both planets follow slightly
elliptical paths around the Sun, so the instant of closest approach
doesn't arrive until May 1st when Mars will pass within 54 million miles of Earth.
By that time Mars will be slightly
dimmer than it was on April 24, but it will appear to be bigger
-- nearly 16 arcseconds across.
That's large enough to reveal details like the north
polar cap, dark surface markings and clouds
to amateurs
viewing the planet through a 6- to 8-inch telescope.
Sky & Telescope has prepared an excellent Mars Observing Guide
which reviews what can likely be seen on the red planet
through a telescope this month.
Martian oppositions occur about once every 26 months, but due
to the elliptical shape of planetary orbits not all oppositions are
the same. This year the apparent diameter of Mars will reach
16 arcseconds, the largest it's been in years, but in
2003 the disk will be a whopping 25 arcseconds across!
That's the maximum size Mars can ever be as seen from Earth.
Experts note that bigger is not always better.
During some of the most anticipated oppositions, such as in 1956,
dust storms on Mars have obscured features from view. On the other
hand,
good Martian weather can lead to crystal clear viewing conditions
when the disk is smaller. The Martian atmosphere was
especially transparent at opposition in February 1995 when the
disk was only 13.6 arcseconds across. Both amateurs and professionals
captured unexpectedly crisp
views of the red planet during that apparition.
Of course the clearest view of Mars this week will be from the
vantage point
of NASA's Mars Global Surveyor (MGS) spacecraft, orbiting just 235 miles above the
planet's surface. Global Surveyor, which reached its final
orbit in February, continues to relay stunning images of ancient
Martian volcanoes, canyons, impact craters, and much more.
While images from the MGS are unmatched for their coverage and
resolution, it's hard to beat a glimpse of the Red Planet at
opposition,
twinkling among the stars on a clear spring night.
As Percival
Lowell noted in his classic book Mars (1895),
"no other heavenly body,
Venus and the Moon alone excepted, ever approaches us so
near..." and although the red planet "is neither new nor
intrinsically great, he possesses for us an interest out of all
proportion to his size or his relative importance in the universe."
Lowell felt the enchantment of Mars
to such a degree that he
devoted his fortune and the latter part of his life
to the study of its mysteries. Was it worth it?
Is the allure of Mars really so powerful?
For the next two weeks you can see for yourself.
Above: Zooming in on Mars. A. A Hubble
Space Telescope View of Mars from 65 million miles distance;
B. A Martian volcano, Apollinaris Patera, with white clouds near the summit
photographed from above by Mars Global Surveyor; C The rock "Barnacle Bill" as seen
from a distance of a few meters at the Mars Pathfinder landing site;
D: Possibly the closest-ever view of Mars.
This high-resolution
electron microscope image shows an unusual tube-like
form less than 1/100th the width of a human hair. It was
found in meteorite ALH84001, believed to be of Martian
origin and is thought by some scientists to be evidence of ancient Martian life. more information.
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