What’s all the hoopla with
Mars?
Elizabeth Warner
UM Observatory
www.astro.umd.edu/openhouse
Mars in the News

Mars to Get Closer than Ever in recorded
History in 2003 (www.space.com)

Mars making closest approach to Earth in
60,000 years (http://www.cnn.com/)
Is this my one chance to see
Mars??
No! Nein! Nyet!
You can see Mars nearly throughout any
given year, you just may have to look at an
odd hour! And Mars will be prominent in the
evening roughly every two years.
So why the hoopla?
Three things happen the week of 25 Aug 2003
 Mars is at perihelion
 Mars is at opposition
 Mars-Earth distance very small
So why is all that important?
 Mars appears bigger, brighter and is visible all
night.
 “full-moon effect”
Elliptical
 Perihelion
 Aphelion
 Opposition

Definitions
Is a circle an ellipse?
Yes, it is the ‘perfect’ ellipse with
eccentricity = 0
What is perigee and apogee?
Hint: Geology, Geography
Bonus: What is periastron?
Hint: Astronomy
So why the hoopla?
Three things happen
the week of 25 Aug
 Mars is at perihelion
 Mars-Earth distance
very small
 Mars is at opposition
Facts
Orbital parameters
Mars
Earth
Sidereal orbit period (days)
686.980
(~22 months)
365.256
Perihelion (106 km)
206.62
147.09
Aphelion (106 km)
249.23
152.10
Synodic period (days)
779.94
(~26 months)
Mean orbital velocity (km/s)
24.13
29.78
Orbit eccentricity
0.0935
0.0167
Length of day (hrs)
24.6597
24.0000
More realistic
The animation starts on 03/21/2001, shortly before
the opposition in 2001, and shows the Earth catching
up to and then passing Mars. The animation
continues through the opposition in 2003 and ends
on the opposition in 2005. Although Mars only takes
about 22 months to go around the sun once, by the
time we catch up to it, it is 4 months further along in
its orbit from the previous opposition, hence the shift
in the position of opposition and why not every
opposition is a close one… just the ones occurring
near Mars’ perihelion point.
Start 03/21/2001
Opposition 06/13/2001
Opposition 08/28/2003
Opposition 11/07/2005
Animation made using Starry Night Pro 4
Date
Angular
size
Distance from
Earth (AU)
2001 Jun 13
20.5”
0.456
2003 Aug 28
25.1”
0.373
2005 Nov 7
19.8”
0.470
The Planet Mars: A History of Observation and Discovery
William Sheehan
Future Oppositions
Other Close Approaches
Rank / Date
Miles Apart
Kilometers
57,617 B.C. Sep. 12
34,622,000
55,718,000
#10 1403 July 31
34,729,759
55,892,131
# 9 1640 Aug. 20
34,716,350
55,870,551
# 8 1198 Aug. 3
34,714,912
55,868,236
# 7 1119 July 31
34,709,476
55,859,488
# 6 1766 Aug. 13
34,696,713
55,838,948
# 5 1561 Aug. 7
34,695,987
55,837,780
# 4 1482 Aug. 3
34,677,852
55,808,594
# 3 1845 Aug. 18
34,674,477
55,803,163
# 2 1924 Aug. 22
34,658,182
55,776,939
# 1 2003 Aug. 27
34,646,418
55,758,006
2287 Aug. 29
34,603,170
55,688,405
So we don’t have to wait another 60,000 years!
Why??

Orbits are not static… they are being
affected by the other planets… Mars’ is
becoming more eccentric…
So Mars is technically closer…
Something far away looks smaller than
same object that is closer.
 Well, if Mars is closer, then it looks bigger
(and brighter).
 If it is bigger, you don’t need as much
‘magnification’ or you can use more and
see more detail.

Why this week?
Actually, many amateurs have already
been observing Mars for several months!
 It is now becoming visible earlier and
earlier in the evenings (rather than having
to get up at 2am!)

Closest approach
09:52 UT 27 Aug 2003
 Opposition
18:00 UT 28 Aug 2003
 Mars at perihelion
~10:45 UT 30 Aug 2003
 It’s all down hill from here!

Visibility zones
evening
Not visible, too
close to the sun!
midnight
morning
Inner planet (Mercury or Venus)
Earth’s orbit
Outer planet (Mars, Jupiter, Saturn,
Uranus, Neptune, or Pluto)
27 Aug 2002!
This and following slides show position of Earth and Mars over several months… can show how Mars was
behind the sun (not visible), then in the morning sky and how it transitions to the evening sky.
30 Dec 2002
30 March 2003
30 June 2003
27 Aug 2003
30 Sep 2003
30 Oct 2003
30 Nov 2003
30 Dec 2003
Mars Images
17 July
“gibbous”
21 Aug 2003
Jeff Forsyth
http://www.teamforsyth.com/mars.html
15 August
Compare to above image…
The “eye” is Solis Lacus
“full Mars”
Mars Previewer II
E. Warner
Notice
- Phase
- Angular size
- Polar cap size
Good Websites
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http://www.theman.themoon.co.uk/Beginners/mars_at_opposition.htm
http://www.uapress.arizona.edu/online.bks/mars/appends.htm
http://www.seds.org/~spider/mars/mars.html
http://www.space.com/spacewatch/mars_10_closest_030822.html
http://www.kidscosmos.org/kid-stuff/mars-oppositions.html
http://www.celestron.com/mars/
http://www.badastronomy.com/bad/news/marsattacks.html
http://skyandtelescope.com/observing/objects/planets/article_970_1.asp
http://skyandtelescope.com/observing/objects/planets/article_997_1.asp
http://www.floridastars.org/marsopp.2003.html