[DOC] [TLE] Mariner 10: First Mission to Mercury - Space.com [PAR] Oct 31, 2012 ... The Mariner 10 spacecraft survived multiple mechanical problems ... It showed 
close-up pictures of the sun's closest planetary neighbor ... 3, 1973, very little was 
known about our neighbors in the solar system. ... Shortly after launch, NASA 
discovered that some television camera heaters were not turned on. [DOC] [TLE] NASA - MESSENGER: The Extreme Machine | NASA [PAR] But many people may not know how the spacecraft is designed in order to get 
there ... Only one NASA spacecraft has visited Mercury and that was Mariner 10 
in 1974 and 1975. It was programmed to fly by the planet three times to take 
images of its ... MESSENGER will determine why Mercury is so much denser and 
more... [DOC] [TLE] Colors of the Innermost Planet, Mercury | NASA [PAR] This colorful view of Mercury was produced by using images from the color base 
... in the flybys of Mariner 10 in the mid-1970s and confirmed by MESSENGER, 
which ... It's exciting to consider that this small planet  not much larger than 
Earth's ... about why some of Mercury's surface looks new, but some appears to 
be old. [DOC] [TLE] Mercury - Views of the Solar System [PAR] Until Mariner 10, little was known about Mercury because of the difficulty in ... 
Although Mercury is not tidally locked to the Sun, its rotational period is tidally ... It 
flew past the planet on March 29, 1974 at a distance of 705 kilometers from ... 
Much of it is old and heavily cratered, but some of the plains are less heavily 
cratered. [DOC] [TLE] Journey to the Innermost Planet [PAR] 1974, when the Mariner 10 space probe ... It was not until 34 years later that we 
finally saw the ... showed the image to the team, everyone cheeredbut ... One 
reason it took three decades to follow up the Mariner 10 mis- ... reach than Jupiter
, even though Jupiter is much farther away. ... Each time, some of the space-. [DOC] [TLE] Mercury (planet) - Wikipedia [PAR] Mercury is the smallest and innermost planet in the Solar System. Its orbital 
period (about 88 Earth days) is less than any other planet in the Solar System. 
Seen from Earth, it appears to move around its orbit in about 116 days. It has no 
known natural satellites. ... Two spacecraft have visited Mercury: Mariner 10 flew 
by in 1974 and 1975;... [DOC] [TLE] Exploration of Mercury - Wikipedia [PAR] The exploration of Mercury has taken only a minor role in the space interests of 
the world. It is the least explored inner planet. As of 2015, the Mariner 10 and 
MESSENGER missions have been the only missions that have made close 
observations of Mercury. MESSENGER made three flybys before entering orbit 
around Mercury. ... Before Mariner 10, astronomers thought that the planet simply 
revolved... [DOC] [TLE] Mercury (Planet) facts, information, pictures | Encyclopedia.com ... [PAR] Mercury is the innermost and second smallest planet (4,878 kilometers ... It has 
no known moons. ... Mariner 10 imaged only about 45 percent of the surface and 
only in ... Because Mercury is so close to the Sun, has no insulating atmosphere, 
and has .... A new color study of Mariner 10 images has been used to derive 
some... [DOC] [TLE] Journey to the Innermost Planet : Article : Scientific American - Nature [PAR] Feb 15, 2011 ... Planetary scientists had a similar feeling on March 29, 1974, when the ... Yet its 
pictures captured only half the basin; the other half remained cloaked in darkness
. ... It was not until 34 years later that we finally saw the entire basin ... This month 
MESSENGER does what Mariner 10 was unable to: it will enter... [DOC] [TLE] Space Today Online - Exploring the planet Mercury [PAR] This was the first image transmitted to Earth following the flyby of Mercury. ... It 
took 10 minutes for radio signals from the small interplanetary probe to ... Unlike 
Mariner 10, MESSENGER eventually will stop and stay a while, settling into orbit 
in 2011. ... side of

Question: Not much was known about this innermost planet until 1974 when Mariner 10 took some pictures
Answer: Mercury