Short answers, pulled from the story.
Mariner 2 was an American robotic space probe launched on the 27th of August 1962. It became the first spacecraft in history to successfully conduct a planetary encounter, flying within 34,773 kilometers of Venus on the 14th of December 1962, and transmitting scientific data back to Earth.
Mariner 2 found that Venus has an extremely hot surface and no significant temperature difference between its day and night sides. It detected limb darkening consistent with a thick cloud layer, found no detectable magnetic field near Venus, and measured atmospheric temperatures suggesting a runaway greenhouse effect.
The Mariner 2 mission lasted 129 days, from its launch on the 27th of August 1962, to the final signal received on the 3rd of January 1963, at 07:00 UTC. After the mission ended, the spacecraft entered a permanent orbit around the Sun.
Mariner 2 carried a two-channel microwave radiometer, a two-channel infrared radiometer, a three-axis fluxgate magnetometer, a cosmic ray detector, a particle detector provided by the University of Iowa, a cosmic dust detector, and a solar plasma spectrometer. The total science payload weighed just 40 pounds due to the limited lift capacity of the Atlas-Agena rocket.
Mariner 2 carried no camera because payload space was severely limited to 40 pounds of scientific instruments, and project scientists deemed a camera unable to return useful scientific results. Carl Sagan, one of the Mariner R scientists, argued unsuccessfully for a camera's inclusion.
During its journey to Venus, Mariner 2 confirmed that the solar wind streams continuously outward from the Sun, validating a prediction by Eugene Parker. It also found that interplanetary dust is far scarcer than scientists had predicted, and measured several solar flares and cosmic rays from outside the Solar System.