Transit of Mercury from Mars
A 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. During a transit, Mercury can be seen from Mars as a small black disc moving across the face of the Sun.
Transits of Mercury from Mars are much more common than transits of Mercury from Earth: there are several per decade.
No one has ever seen a transit of Mercury from Mars, but they could be observed by future Mars colonists.
The Mars Rovers Spirit and Opportunity could have observed the transit on January 12, 2005 (from 14:45 UTC to 23:05 UTC); however the only available for this had insufficient resolution. They were able to observe transits of Deimos across the Sun, but at 2' angular diameter, Deimos is about 20 times larger than Mercury's 6.1" angular diameter. Ephemeris data generated by JPL Horizons indicates that Opportunity would be able to observe the transit from the start until local sunset at about 19:23 UTC, while Spirit would be able to observe it from local sunrise at about 19:38 UTC until the end of the transit.
The Mercury-Mars synodic period is 100.888 days. It can be calculated using the formula 1/(1/P-1/Q), where P is the orbital period of Mercury (87.969 days) and Q is the orbital period of Mars (686.98 days).
The inclination of Mercury's orbit with respect to that of Mars is 5.16°, which is less than its value of 7.00° with respect to Earth's ecliptic.
|December 18, 2003||July 13, 2044||January 12, 2084|
|January 12, 2005||May 24, 2045||November 22, 2084|
|November 23, 2005||November 8, 2052||May 9, 2092|
|May 10, 2013||December 3, 2053||June 3, 2093|
|June 4, 2014||October 14, 2054||April 14, 2094|
|April 15, 2015||April 25, 2063|
|October 25, 2023||March 6, 2064|
|September 5, 2024||July 27, 2073|
|January 26, 2034||August 22, 2074|
|February 21, 2035||December 17, 2082|
Transit visibility table
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The simultaneous occurrence of a transit of Mercury and a transit of Venus is extremely rare, but somehow more frequent than from Earth, and will next occur in the years 18,713, 19,536 and 20,029.
On several occasions an almost identical event is predicted: a transit of Mercury and a transit of Venus, or transit of Earth will follow themselves, one after the other, in an interval of only several hours.
On November 28, 3867 there is a transit of Earth and Moon, and two days later a transit of Mercury occurs. On January 16, 18551 transits of Mercury and Venus are separated by 14 hours.
- Albert Marth, Note on the Transit of the Earth and Moon across the Sun’s Disk as seen from Mars on November 12, 1879, and on some kindred Phenomena, Monthly Notices of the Royal Astronomical Society, 39 (1879), 513–514. 
- Giorgini, J.D., Yeomans, D.K., Chamberlin, A.B., Chodas, P.W., Jacobson, R.A., Keesey, M.S., Lieske, J.H., Ostro, S.J., Standish, E.M., Wimberly, R.N., "JPL's On-Line Solar System Data Service", Bulletin of the American Astronomical Society 28(3), 1158, 1996.