Editing Astronomical transit (section)

== In the Solar System ==
[[File:Jupiter-io-transit feb 10 2009.gif|thumb|A simulation of Io transiting Jupiter as seen from the Earth in February 2009. Io's shadow is seen on the surface of Jupiter, leading Io slightly due to the Sun and Earth not being in the same line.]]
One type of transit involves the motion of a [[planet]] between a [[Earth|terrestrial]] observer and the [[Sun]]. This can happen only with [[inferior and superior planets|inferior planets]], namely [[Mercury (planet)|Mercury]] and [[Venus]] (see [[transit of Mercury]] and [[transit of Venus]]). However, because a transit is dependent on the point of observation, the [[transit of Earth from Mars|Earth itself transits the Sun]] if observed from Mars. In the solar transit by the [[Moon]] captured during calibration of the [[STEREO]] B spacecraft's ultraviolet imaging, the Moon appears much smaller than it does when seen from [[Earth]], because the spacecraft–Moon separation was several times greater than the [[lunar distance (astronomy)|Earth–Moon distance]].

The term can also be used to describe the motion of a [[natural satellite|satellite]] across its parent planet, for instance one of the Galilean satellites ([[Io (moon)|Io]], [[Europa (moon)|Europa]], [[Ganymede (moon)|Ganymede]], [[Callisto (moon)|Callisto]]) across [[Jupiter]], as seen from [[Earth]].

Although rare, cases where four bodies are lined up do happen. One of these events occurred on 27 June 1586, when Mercury transited the Sun as seen from Venus at the same time as a transit of Mercury from Saturn and a transit of Venus from Saturn. {{Citation needed|date=June 2017}}

=== Notable observations ===
No missions were planned to coincide with the transit of [[Earth]] visible from [[Mars]] on 11 May 1984 and the Viking missions had been terminated a year previously. Consequently, the next opportunity to observe such an alignment will be in 2084.

On 21 December 2012, the ''[[Cassini–Huygens]]'' probe, in orbit around [[Saturn]], observed the planet [[Venus]] transiting the Sun.<ref>''[http://spacecoastdaily.com/2012/12/cassini-spacecraft-tracks-venus-transit-from-saturn/ Cassini Spacecraft Tracks Venus Transit From Saturn]'', Space Coast Daily. Retrieved on 8 February 2016.</ref>

On 3 June 2014, the Mars rover [[Curiosity (rover)|''Curiosity'']] observed the planet [[Mercury (planet)|Mercury]] transiting the Sun, marking the first time a [[planetary transit]] has been observed from a celestial body besides Earth.<ref name="NASA-20140610">{{cite web|url=http://www.jpl.nasa.gov/news/news.php?release=2014-183|title=Mercury Passes in Front of the Sun, as Seen From Mars|last=Webster|first=Guy|date=10 June 2014|work=[[NASA]]}}</ref>

=== Mutual planetary transits ===
{{main|Planetary transits and occultations}}
In rare cases, one planet can pass in front of another. If the nearer planet appears smaller than the more distant one, the event is called a ''mutual planetary transit''.<gallery>
File:2012 Transit of Venus from SF.jpg|Transit of Venus as seen from Earth, 2012
File:PIA02879 - A New Year for Jupiter and Io.jpg|[[Io (moon)|Io]] transits across [[Jupiter]] as seen by ''[[Cassini-Huygens|Cassini]]'' spacecraft
File:PIA18389-MarsCuriosityRover-MercuryTransitsSun-20140603.gif|Mercury transiting the Sun, seen from [[Curiosity (rover)|''Curiosity'']] rover on Mars (3 June 2014).
File:Dark side of the Moon.png|The Moon transiting in front of Earth, seen by Deep Space Climate Observatory on 4 August 2015.
</gallery>