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Transit of Deimos from Mars

From Academic Kids

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13-ml-04-deimos-A067R1.jpg
Deimos transits the Sun, as seen by Mars Rover Opportunity on March 4 2004

A transit of Deimos across the Sun as seen from Mars takes place when Deimos passes directly between the Sun and a point on the surface of Mars, obscuring a small part of the Sun's disc for an observer on Mars. During a transit, Deimos can be seen from Mars as a small black disc rapidly moving across the face of the Sun.

The event could also be referred to as a partial eclipse of the Sun by Deimos. However, since the angular diameter of Deimos is only about 1/10 of the angular diameter of the Sun as seen from Mars, it is more natural to refer to it as a transit. The angular diameter of Deimos is only 2 1/2 times the angular diameter of Venus from Earth during a transit of Venus from Earth.

A transit of Deimos from Mars usually lasts only a minute or two, due to its relatively rapid orbital period of about 30.3 hours.

Because they orbit Mars in low-inclination equatorial orbits, the shadows of Phobos or Deimos projected onto the surface of Mars exhibit a seasonal variation in latitude. At any given geographical location on the surface of Mars, there are two intervals in a Martian year when the shadows of Phobos or Deimos are passing through its latitude. During each such interval, zero or one transits of Deimos can be seen by observers at that geographical location (compared to about half a dozen transits of Phobos).

It is easy to see that the shadow always falls on the "winter hemisphere", except when it crosses the equator during the vernal equinox and the autumnal equinox. Thus transits of Deimos happen during Martian autumn and winter in the northern hemisphere and the southern hemisphere, roughly symmetrically around the winter solstice. Close to the equator they happen around the autumnal equinox and the vernal equinox; farther from the equator they happen closer to the winter solstice.

Because it orbits relatively close to Mars, Deimos cannot be seen north of 82.7N or south of 82.7S; such latitudes will obviously not see transits either.

On March 4 2004 a transit was photographed by Mars Rover Opportunity, while on March 13 2004 a transit was photographed by Mars Rover Spirit. In the captions below, the first row shows Earth time UTC and the second row shows Martian local solar time.


March 4 2004 transit from Opportunity
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Deimos_Mar_04_2004_from_Opportunity_1.jpg
Image:Deimos_Mar_04_2004_from_Opportunity_1.jpg

Image:Deimos_Mar_04_2004_from_Opportunity_2.jpg Image:Deimos_Mar_04_2004_from_Opportunity_3.jpg Missing image
Deimos_Mar_04_2004_from_Opportunity_4.jpg
Image:Deimos_Mar_04_2004_from_Opportunity_4.jpg

03:03:43
10:28:17
03:03:53
10:28:27
03:04:03
10:28:36
03:04:13
10:28:46
March 13 2004 transit from Spirit
Image:Deimos_Mar_13_2004_from_Spirit_1.jpg Missing image
Deimos_Mar_13_2004_from_Spirit_2.jpg
Image:Deimos_Mar_13_2004_from_Spirit_2.jpg

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Deimos_Mar_13_2004_from_Spirit_3.jpg
Image:Deimos_Mar_13_2004_from_Spirit_3.jpg

Image:Deimos_Mar_13_2004_from_Spirit_4.jpg Image:Deimos_Mar_13_2004_from_Spirit_5.jpg Missing image
Deimos_Mar_13_2004_from_Spirit_6.jpg
Image:Deimos_Mar_13_2004_from_Spirit_6.jpg

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Deimos_Mar_13_2004_from_Spirit_7.jpg
Image:Deimos_Mar_13_2004_from_Spirit_7.jpg

Image:Deimos_Mar_13_2004_from_Spirit_8.jpg
00:04:27
13:54:11
00:04:37
13:54:20
00:04:47
13:54:30
00:04:57
13:54:40
00:05:07
13:54:50
00:05:17
13:54:59
00:05:27
13:55:09
00:05:37
13:55:19
March 9 2005 transit from Spirit
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Deimos_Mar_09_2005_from_Spirit_01.jpg
Image:Deimos Mar 09 2005 from Spirit 01.jpg

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Deimos_Mar_09_2005_from_Spirit_02.jpg
Image:Deimos Mar 09 2005 from Spirit 02.jpg

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Deimos_Mar_09_2005_from_Spirit_03.jpg
Image:Deimos Mar 09 2005 from Spirit 03.jpg

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Deimos_Mar_09_2005_from_Spirit_04.jpg
Image:Deimos Mar 09 2005 from Spirit 04.jpg

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Deimos_Mar_09_2005_from_Spirit_05.jpg
Image:Deimos Mar 09 2005 from Spirit 05.jpg

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Deimos_Mar_09_2005_from_Spirit_06.jpg
Image:Deimos Mar 09 2005 from Spirit 06.jpg

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Deimos_Mar_09_2005_from_Spirit_07.jpg
Image:Deimos Mar 09 2005 from Spirit 07.jpg

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Deimos_Mar_09_2005_from_Spirit_08.jpg
Image:Deimos Mar 09 2005 from Spirit 08.jpg

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Deimos_Mar_09_2005_from_Spirit_09.jpg
Image:Deimos Mar 09 2005 from Spirit 09.jpg

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Deimos_Mar_09_2005_from_Spirit_10.jpg
Image:Deimos Mar 09 2005 from Spirit 10.jpg

Missing image
Deimos_Mar_09_2005_from_Spirit_11.jpg
Image:Deimos Mar 09 2005 from Spirit 11.jpg

15:58:19 15:58:29 15:58:39 15:58:49 15:58:59 15:59:09 15:59:19 15:59:29 15:59:39 15:59:49 15:59:59

The data is the tables below is generated using JPL Horizons (http://ssd.jpl.nasa.gov/horizons.html). There is some discrepancy of a minute or two with the times reported for the series of images above. This may be due to imprecision in the ephemeris data used by JPL Horizons; also the JPL Horizons data gives local apparent solar time while the times reported above are probably some form of mean solar time (and therefore some of the discrepancy would be due to the Martian equivalent of the equation of time).

Note: the data below are valid for the original landing sites. To the extent that the rovers have moved around on the surface, the parameters of the transits as actually observed may be slightly different.

Near misses are indicated with strikeout.

Transits of Deimos from Mars Rover Spirit landing site
Duration
Earth time (UTC)
Duration
(Local Solar time)
Minim.
separ.
Deimos
ang. diam.
Sun
ang. diam.
Sun
alt.
April 24 2003
03:05:36
10 12 59 888.8" 151.0" 1296.4" 58.3°
April 25 2003
(10:22:29 – 10:24:25)
16 39 46 – 16 41 39 248.4" 139.6" 1297.8" 18.5°
March 13 2004
(00:05:06 – 00:06:35)
13 56 12 – 13 57 39 458.6" 150.6" 1225.0" 56.8°
March 9 2005
(15:54:16 – 15:56:14)
14 49 07 – 14 51 02 261.4" 147.6" 1294.5" 44.3°
January 26 2006
05:28:45
11 57 05 1509.5" 153.4" 1227.9" 74.0°
January 22 2007
21:19:39
12 52 10 982.8" 152.6" 1291.6" 67.8°
December 12 2007
18:10:49
16 26 33 850.0" 140.9" 1229.2" 22.3°


Transits of Deimos from Mars Rover Opportunity landing site
Duration
Earth time (UTC)
Duration
(Local Solar time)
Minim.
separ.
Deimos
ang. diam.
Sun
ang. diam.
Sun
alt.
May 30 2003
(00:06:57 – 00:09:04)
13 28 59 – 13 31 02 95.8" 152.5" 1306.3" 67.3°
March 4 2004
(03:03:52 – 03:05:06)
10 30 14 – 10 31 25 550.0" 152.6" 1233.6" 67.6°
March 5 2004
10:21:52
16 58 21 1041.5" 138.6" 1232.3" 15.4°
March 17 2005
05:28:44
11 28 40 1041.8" 154.0" 1303.0" 81.6°
March 18 2005
(12:36:42 – 12:38:43)
17 46 46 – 17 48 43 89.6" 134.3" 1304.4" 3.0°
January 18 2006
(15:54:26 – 15:56:21)
15 08 00 – 15 09 52 198.4" 147.2" 1235.3" 42.7°
January 31 2007
18:15:01
16 02 28 824.8" 143.2" 1301.4" 29.3°
December 3 2007
21:20:36
13 11 25 739.0" 153.1" 1238.0" 72.1°

See also

Reference

  • J. Bell, M. Lemmon, M. Wolff, Transits of Mars I and II, IAU Circ., 8298, 2 (2004). [1] (http://cfa-www.harvard.edu/iauc/08200/08298.html) (TeX DVI file is at [2] (http://cfa-www.harvard.edu/iauc/08200/08298.dvi)).

External links

  • JPL Horizons (http://ssd.jpl.nasa.gov/horizons.html) (must use telnet interface for non-Earth observation points)
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