Transit of Deimos from Mars
Encyclopedia
Mars
Mars is the fourth planet from the Sun in the Solar System. The planet is named after the Roman god of war, Mars. It is often described as the "Red Planet", as the iron oxide prevalent on its surface gives it a reddish appearance...
takes place when Deimos
Deimos (moon)
Deimos is the smaller and outer of Mars's two moons . It is named after Deimos, a figure representing dread in Greek Mythology. Its systematic designation is '.-Discovery:Deimos was discovered by Asaph Hall, Sr...
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
Astronomical transit
The term transit or astronomical transit has three meanings in astronomy:* A transit is the astronomical event that occurs when one celestial body appears to move across the face of another celestial body, hiding a small part of it, as seen by an observer at some particular vantage point...
, 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
Eclipse
An eclipse is an astronomical event that occurs when an astronomical object is temporarily obscured, either by passing into the shadow of another body or by having another body pass between it and the viewer...
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 2½ times the angular diameter of Venus
Venus
Venus is the second planet from the Sun, orbiting it every 224.7 Earth days. The planet is named after Venus, the Roman goddess of love and beauty. After the Moon, it is the brightest natural object in the night sky, reaching an apparent magnitude of −4.6, bright enough to cast shadows...
as seen from Earth during a transit of Venus from Earth
Transit of Venus
A transit of Venus across the Sun takes place when the planet Venus passes directly between the Sun and Earth, becoming visible against the solar disk. During a transit, Venus can be seen from Earth as a small black disk moving across the face of the Sun...
.
A transit of Deimos from Mars lasts a maximum of about two minutes, due to its relatively rapid orbital period
Orbital period
The orbital period is the time taken for a given object to make one complete orbit about another object.When mentioned without further qualification in astronomy this refers to the sidereal period of an astronomical object, which is calculated with respect to the stars.There are several kinds of...
of about 30.3 hours.
Because they orbit Mars in low-inclination equatorial orbits, the shadows of Phobos
Phobos (moon)
Phobos is the larger and closer of the two natural satellites of Mars. Both moons were discovered in 1877. With a mean radius of , Phobos is 7.24 times as massive as Deimos...
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
Transit of Phobos from Mars
A transit of Phobos across the Sun as seen from Mars takes place when Phobos passes directly between the Sun and a point on the surface of Mars, obscuring a large part of the Sun's disc for an observer on Mars. During a transit, Phobos can be seen from Mars as a large black disc rapidly moving...
).
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
Solstice
A solstice is an astronomical event that happens twice each year when the Sun's apparent position in the sky, as viewed from Earth, reaches its northernmost or southernmost extremes...
. 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 82.7°N or south of 82.7°S; 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
Timekeeping on Mars
Various schemes have been used or proposed to keep track of time and date on the planet Mars independently of Earth time and calendars.Mars has an axial tilt and a rotation period similar to those of Earth. Thus it experiences seasons of spring, summer, autumn and winter much like Earth, and its...
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| 03:03:43 10:28:17 |
03:03:53 10:28:27 |
03:04:03 10:28:36 |
03:04:13 10:28:46 |
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| 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 |
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| 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 in the tables below is generated using JPL Horizons. 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
Equation of time
The equation of time is the difference between apparent solar time and mean solar time. At any given instant, this difference will be the same for every observer...
).
Note: the data below is 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 in italics.
| 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
- Solar eclipses on MarsSolar eclipses on MarsThe two moons of Mars—Phobos and Deimos— are much smaller than the Earth's moon, greatly reducing solar eclipses on that planet.-Eclipses caused by Phobos:...
- Astronomy on MarsAstronomy on MarsThe Astronomy on Mars article presents information and images about viewing astronomical phenomena from the planet Mars. In many cases these are the same or similar to those seen from Earth but sometimes they can be quite different...
- Transit of Mercury from MarsTransit of Mercury from MarsA transit of Mercury across the Sun as seen from Mars takes place when the planet Mercury passes directly between the Sun and Mars, obscuring a small part of the Sun's disc for an observer on Mars...
- Transit of Venus from MarsTransit of Venus from MarsA transit of Venus across the Sun as seen from Mars takes place when the planet Venus passes directly between the Sun and Mars, obscuring a small part of the Sun's disc for an observer on Mars...
- Transit of Earth from MarsTransit of Earth from MarsA transit of Earth across the Sun as seen from Mars takes place when the planet Earth passes directly between the Sun and Mars, obscuring a small part of the Sun's disc for an observer on Mars. During a transit, Earth can be seen from Mars as a small black disc moving across the face of the Sun...
- Transit of Phobos from MarsTransit of Phobos from MarsA transit of Phobos across the Sun as seen from Mars takes place when Phobos passes directly between the Sun and a point on the surface of Mars, obscuring a large part of the Sun's disc for an observer on Mars. During a transit, Phobos can be seen from Mars as a large black disc rapidly moving...
Further reading
- J. Bell, M. Lemmon, M. Wolff, Transits of Mars I and II, IAU Circ., 8298, 2 (2004).
http://www.cbat.eps.harvard.edu/iauc/08200/08298.html(TeXTeXTeX is a typesetting system designed and mostly written by Donald Knuth and released in 1978. Within the typesetting system, its name is formatted as ....
DVI file is at http://www.cbat.eps.harvard.edu/iauc/08200/08298.dvi).
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).
- Spirit image gallery: Sol 420 (small images of the March 9, 2005 transit are near the middle of the page).
- Animation of March 4 2004 transit