The Space Age had started less than a month before, with the launch of the first Soviet satellite on October 4, 1957. Sputnik 1, a 40-pound sphere, carried a simple transmitter and was considered very heavy compared to the U.S. spacecraft under development at the time.
Enter Sputnik 2. The Soviet press boasted about the 250-pound object equipped with a cabin, providing all the necessary life support for a dog named Laika. Well, almost. The Soviets admitted soon after the launch that the spacecraft would not return, meaning that the animal was doomed from the start. Years after Sputnik 2 burned up in the atmosphere, conflicting scenarios of Laika’s death were circulating in the West.
Wikipedia’s entry on Laika and Sputnik 2.