Transit of Deimos from Mars
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.
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.
For any one fixed spot on the surface of Mars, transits of Deimos are relatively rare, and can occur on no more than two windows of opportunity per Martian year; sometimes a window of opportunity produces only a near miss rather than a transit, or a suitable transit may take place while the Sun is below the horizon. By contrast, transits (or partial eclipses) of Phobos are much more common.
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.
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| 10:28:17 | 10:28:27 | 10:28:36 | 10:28:46 |
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| 13:54:11 | 13:54:20 | 13:54:30 | 13:54:40 | 13:54:50 | 13:54:59 | 13:55:09 | 13:55:19 |
The data is the tables below is generated using JPL Horizons. It is not clear why the local solar times of transit for the March 4 and March 13 events differ by a couple of Martian minutes from the times reported for the series of images above. Perhaps it's the Martian equivalent of the equation of time.
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. |
03:05:36 |
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° |
05:28:45 |
1509.5" | 153.4" | 1227.9" | 74.0° | |
21:19:39 |
982.8" | 152.6" | 1291.6" | 67.8° | |
18:10:49 |
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° |
10:21:52 |
1041.5" | 138.6" | 1232.3" | 15.4° | |
05:28:44 |
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° |
18:15:01 |
824.8" | 143.2" | 1301.4" | 29.3° | |
21:20:36 |
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](this circular is not available online, and I don't have access to a paper copy). (Lookup at [2])
External links
- JPL Horizons (must use telnet interface for non-Earth observation points)
- Opportunity image gallery: Sol 39 (small images of the March 4 2004 transit are near the bottom of the page).
- Spirit image gallery: Sol 68 (small images of the March 13 2004 transit are near the bottom of the page).