Physical properties of Mars Rotation

Mars' physical properties are listed in Table 1.4. Mars' sidereal rotation period is 24h 37m 22.65s, slightly longer than the terrestrial period of 23h 56m 4.09s. The

Table 1.3 Mars oppositions (2000-2020)

Opposition date

Closest approach date

Closest distance (106km)

Apparent diameter (arcseconds)

2001 June 13

June 21

67.34

20.79

2003 August 28

August 27

55.76

25.11a

2005 November 7

October 30

69.42

20.19

2007 December 24

December 18

88.17

15.88

2010 January 29

January 27

99.3

14.1

2012 March 3

March 5

100.8

13.9b

2014 April 8

April 14

92.4

15.2

2016 May 22

May 30

75.3

18.6

2018 July 27

July 31

57.6

24.3

2020 October 13

October 6

62.2

22.6

a Perihelic opposition. b Aphelic opposition.

Source: Students for the Exploration and Development of Space (SEDS) website: www.seds.org/~spider/spider/Mars/marsopps.html

Table 1.4 Physical properties of Mars

Mass

Volume

Mean density

Mean radius

Mean equatorial radius

North polar radius

South polar radius

Sidereal rotation period

Solar day

Flattening

Precession rate

Surface gravity

Escape velocity

Bond albedo

Visual geometric albedo

Blackbody temperature

6.4185 x1023kg 1.6318 x10nkm3 3933kg m-3 3389.508km 3396.200km 3376.189km 3382.580km 24.622958 h 24.659722 h 0.00648

-7576 milli-arcseconds yr 3.71ms-2 5.03km s-1

Source: Data from Smith et al. (2001a) and NSSDC Mars Fact Sheet: nssdc.gsfc.nasa.gov/planetary/factsheet/marsfact.html direction of rotation is the same as on Earth, counterclockwise as seen from above the ecliptic. The Earth's solar day is defined to be exactly 24h; Mars' solar day is 24h 39m 35s and is called a "sol." In the remainder of this book, we will use the term "days" to refer to Earth days and "sols" to refer to Mars days.

Mars' rotation axis undergoes precession due to the gravitational influences of the other planets. From observed changes in the martian rotation rate measured by the Viking landers in the 1970s and the Mars Pathfinder mission in 1997, the precession rate is -7576±35 milli-arcseconds per year (Folkner et al., 1997). The rate of change of right ascension in the martian equatorial coordinate system due to precession is -0.1061° per century and the rate of change of declination is -0.0609° per century (Folkner et al., 1997).

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