What’s all the hoopla with Mars? Elizabeth Warner UM Observatory

Mars in the News Mars to Get Closer than Ever in recorded History in 2003 ( Mars making closest approach to Earth in 60,000 years (

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”

Definitions Elliptical Perihelion Aphelion Opposition What is perigee and apogee? Hint: Geology, Geography Bonus: What is periastron? Hint: Astronomy Is a circle an ellipse? Yes, it is the ‘perfect’ ellipse with eccentricity = 0

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 MarsEarth Sidereal orbit period (days) (~22 months) Perihelion (10 6 km) Aphelion (10 6 km) Synodic period (days) (~26 months) Mean orbital velocity (km/s) Orbit eccentricity Length of day (hrs)

More realistic Start 03/21/2001 Opposition 06/13/2001 Opposition 08/28/2003 Opposition 11/07/2005 Animation made using Starry Night Pro 4 The Planet Mars: A History of Observation and Discovery William Sheehan DateAngular size Distance from Earth (AU) 2001 Jun ” Aug ” Nov 719.8”0.470 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 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.

Future Oppositions

Other Close Approaches Rank / DateMilesKilometers 57,617 B.C. Sep. 1234,622,00055,718,000 # July 3134,729,75955,892,131 # Aug. 2034,716,35055,870,551 # Aug. 334,714,91255,868,236 # July 3134,709,47655,859,488 # Aug. 1334,696,71355,838,948 # Aug. 734,695,98755,837,780 # Aug. 334,677,85255,808,594 # Aug. 1834,674,47755,803,163 # Aug. 2234,658,18255,776,939 # Aug. 2734,646,41855,758, Aug. 2934,603,17055,688,405 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 approach09:52 UT 27 Aug 2003 Opposition18:00 UT 28 Aug 2003 Mars at perihelion~10:45 UT 30 Aug 2003 It’s all down hill from here!

Visibility zones evening morning midnight Not visible, too close to the sun! 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 21 Aug 2003 Jeff Forsyth 17 July 15 August E. Warner Notice - Phase - Angular size - Polar cap size Mars Previewer II Compare to above image… The “eye” is Solis Lacus “gibbous” “full Mars”

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