Transit of Earth from Mars
Encyclopedia
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...
of Earth across the Sun as seen from Mars takes place when the planet Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
passes directly between the Sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
and Mars
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...
, 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. A central transit may last up over 10 hours, although this is extremely rare (the last time it happened was in 2277 BC, and the next one is in 5003 AD). It occurs every 26, 79 and 100 years, yet around every 1,000 years or so an extra 53rd-year transit occurs.
Conjunctions
Transits of Earth from Mars usually occur in pairs, with one following the other after 79 years; rarely, there are three in the series. The transits also follow a 284-year cycle, occurring at intervals of 100.5, 79, 25.5, and 79 years; a transit falling on a particular date is usually followed by another transit 284 years later. Transits occurring when Mars is at its ascending node are in May, those at descending node happen in November. This cycle corresponds fairly closely to 151 Mars orbits, 284 Earth orbits, and 133 synodic periods, and is analogous to the cycle of transits of Venus from EarthTransit 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...
, which follow a cycle of 243 years (121.5, 8, 105.5, 8). There are currently four such active series, containing from 8 to 25 transits. A new one is set to begin in 2394. The last series ending was in 1211.
View from Mars
No one has ever seen a transit of Earth from Mars, but the next one will take place on November 10, 2084, and could be observed by future Mars colonists. The last such transit took place on May 11, 1984.During the event, the Moon
Moon
The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...
could almost always also be seen in transit, although due to the distance between Earth and Moon, sometimes one body completes the transit before the other begins (this last occurred in the 1800 transit, and will happen again in 2394).
View from Earth
A transit of Earth from Mars corresponds to Mars being perfectly uniformly illuminated at opposition from Earth, its phase being 180.0° without any defect of illumination. During the 1879 event, this permitted Charles Augustus YoungCharles Augustus Young
Charles Augustus Young was an American astronomer.He graduated from Dartmouth and later became a professor there in 1865, remaining until 1877 when he went to Princeton....
to attempt a careful measurement of the oblateness (polar compression) of Mars. He obtained the value 1/219, or 0.0046. This is close to the modern value of 1/154 (many sources will cite somewhat different values, such as 1/193, because even a difference of only a couple of kilometers in the values of Mars' polar and equatorial radii gives a considerably different result).
In science fiction
A science fictionScience fiction
Science fiction is a genre of fiction dealing with imaginary but more or less plausible content such as future settings, futuristic science and technology, space travel, aliens, and paranormal abilities...
short story published in 1971 by Sir Arthur C. Clarke
Arthur C. Clarke
Sir Arthur Charles Clarke, CBE, FRAS was a British science fiction author, inventor, and futurist, famous for his short stories and novels, among them 2001: A Space Odyssey, and as a host and commentator in the British television series Mysterious World. For many years, Robert A. Heinlein,...
, called "Transit of Earth", depicts a doomed astronaut on Mars observing the transit in 1984. This short story was first published in the January 1971 issue of Playboy
Playboy
Playboy is an American men's magazine that features photographs of nude women as well as journalism and fiction. It was founded in Chicago in 1953 by Hugh Hefner and his associates, and funded in part by a $1,000 loan from Hefner's mother. The magazine has grown into Playboy Enterprises, Inc., with...
magazine.
Dates of transits
| November 10, 1595 |
| May 5, 1621 |
| May 8, 1700 |
| November 9, 1800 |
| November 12, 1879 |
| May 8, 1905 |
| May 11, 1984 |
| November 10, 2084 |
| November 15, 2163 |
| May 10, 2189 |
| May 13, 2268 |
| November 13, 2368 |
| May 10, 2394 |
| November 17, 2447 |
| May 13, 2473 |
| November 2552 |
| November 2578 |
Grazing and simultaneous transits
Sometimes Earth only grazes the Sun during a transit. In this case it is possible that in some areas of Mars a full transit can be seen while in other regions there is only a partial transit (no second or third contact). The last transit of this type was on 30 April 1211, and the next such transit will occur on 27 November 43565th millennium
The fifth millennium is a period of time that will begin on January 1, 4001, and will end on December 31, 5000.-Astronomical events:* 4285 : Venus occults Regulus.* 4296 : Venus occults Antares....
. It is also possible that a transit of Earth can be seen in some parts of Mars as a partial transit, while in others Earth misses the Sun. Such a transit last occurred on 26 October 664, and the next transit of this type will occur on 14 December 5934
6th millennium
The sixth millennium is a period of time that will begin on January 1, 5001, and will end on December 31, 6000.-Astronomical events:* 5001 September 11: Mercury occults Regulus* c...
.
The simultaneous occurrence of a transit of Venus
Transit of Venus from Mars
A 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...
and a transit of Earth is extremely rare, and will next occur in the year 571,471.
See also
- Astronomical transitAstronomical transitThe 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...
- 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...
- Transit of Deimos from MarsTransit of Deimos from MarsA 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...