Mars - up close!
Mars will be closer to Earth on 27 August than it has been in nearly 60,000
years. It will be nearly three centuries before it is this close again.
On 27 August 2003 at 11:51 SAST, the centres of Earth and Mars will be only
55,758,006 km apart, according to both the U.S. Naval Observatory and NASA's Jet
Propulsion Laboratory. The last time Mars came this close to Earth was 57617 BC,
when Mars came within 55,718 million km from the Earth. The next time Mars will
be this close will be in 2287.
With the Naked Eye: a Bright Orange Star
What this means is that Mars will appear much brighter than usual this
August, outshining all the stars, and all the planets except Venus (which isn't
visible this month). Look for a bright orange 'star' in the east (evening sky)
or in the west (morning sky before sunrise). If you watch Mars in the dawn, you
may be able to see the planet even after the sun rises. Mars is BRIGHT this
August!
Through the Telescope: the Mouldy Naartjie
 Through a good telescope when the skies are clear and the atmosphere is
'steady' (not too many air currents like those that blur the view across a hot
parking lot), it should be possible to see Mars' bright polar cap, yellow-orange
deserts and dark patches - about as much detail as you can see on the full moon
without a telescope. Mars through a telescope looks like nothing so much as a
mouldy naartjie.
Why So Bright? A Passing Fancy
Mars is the 4th planet from the sun; Earth is the 3rd. Because Earth is
closer to the sun, it moves faster in its orbit than Mars does, and passes Mars
('lapping' Mars like a faster race car on a separate inside track) once every 26
months. That moment is when we make our closest approach to Mars for that
26-month period, and when Mars looks brightest from Earth. When Earth and Mars
are on opposite sides of the sun, Mars is at its most distant and looks
relatively dim. But our two planetary race cars don't follow circular tracks
around the sun. Both follow elliptical tracks that carry them much closer to the
sun sometimes than others. If Mars is near its greatest distance from the sun,
and Earth is near its least distance from the sun when Earth 'laps' Mars, then
the closest approach distance between the two planets will be nearly twice as
great as it will be this August. This is what happened in February 1995.
If Earth is near its greatest distance from the sun, and Mars is near its
least distance from the sun, the two planets can make a much closer approach
than average. This happens every 15 to 17 years, and 27 August, 2003 is a
particularly good example.
See http://www.saao.ac.za/news/aug_2003.jpg to view Mars orbit.
But why does Mars come closer this year than in
nearly 60,000 years?
Over thousands of years, the shape of Mars' orbit slowly changes. Mars now
makes slightly closer approaches to the sun than it did when the Pyramids were
built, or in 20000 BC. In 2287, Mars will come even nearer than it does this
year (though only by a hair), and in 2650 and 2729 will come closer still.
Sending the Robot FleetBut humanity isn't content with the view from Earth, even
this August. An entire fleet of spacecraft is cruising toward the Red
Planet.
In December/January, four robotic spacecraft will arrive, ready to explore.
Two space probes are already in orbit around Mars: Global Surveyor and Odyssey.
Two more orbiters are on the way: Japan's Nozomi and Europe's Mars Express.
Three probes are scheduled to land on Mars. Britain's Beagle (riding to the Red
Planet with Mars Express) will do laboratory tests on Martian rocks/soil near
the equator, while NASA's Opportunity and Spirit 'rovers' (each the size of a
small golf cart) will land and move around the surface as much as 100 metres per
day. Five space probes have never arrived at any other planet in such a short
time.
But Mars is special. It fascinates us because although it has air only 1% as
dense as ours, no breathable oxygen, cold so intense that 'dry ice' caps form at
the poles, and no liquid water (but lots of ice) - it's still the most Earthlike
planet in our solar system. Take a look as it swings by.
More information
Contact: Email Dave Laney at SAAO.
Information from South African Astronomical Observatory.
SAAO, Cape Town will host special Mars Open Evenings on 27 August at 20h30,
30 August at 20h15 and 3 September at 20h00 including slides and Mars viewing
through a telescope (weather permitting). Those wishing to visit the SAAO should
phone (021) 447-0025 to book for any of these evenings.
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