|Earth Pre-Federation Database - Mariner 2|
|Mariner 2 was an American Mariner program space probe that was in service with NASA in the mid-20th century. A schematic of this probe was
stored in the USS Enterprise's library computer database. This database was accessed by the Talosians in 2254.
TOS "The Cage"
On December 14, 1964, Mariner 2 successfully performed the first planetary encounter of a space probe when it passed within 35,000 kilometers of the planet Venus. This probe surveyed Venus revealing that this planet has a very hot surface blanketed by a thick cloud cover.
The design of Mariner 2 was based off the Ranger Block I space probe. This spacecraft was launched into space on an Atlas-Agena rocket.
Text from the Memory Alpha, the free Star Trek reference