Heart murmur. Heart murmurs are heart sounds produced when blood flows across one of the heart valves that are loud enough to be heard with a stethoscope. There are two types of murmurs. A functional murmur or physiologic murmur is a heart murmur that is primarily due to physiologic conditions outside the heart. Other types of murmurs are due to structural defects in the heart itself.
Voyager 2 passed Neptune in the summer of 1989, the first spacecraft to observe that planet. Passing about 3,000 miles above Neptune's north pole, Voyager 2 made its closest approach to any planet since it left Earth 12 years earlier.
Artist's concept of Mariner 9, the first probe to orbit Mars. Image credit: NASA We received this question from fourth-grade students in Fresno, California. JPL's Homework Help page provides basic information and suggestions for further research. A probe is a spacecraft that travels through space to collect science information. Probes do not have astronauts. Probes send data back to Earth for scientists to study. The First Probes Sputnik 1 was the first probe to go into space. It was launched on Oct. 4, 1957, by the former Soviet Union. On Jan. 31, 1958, the United States sent a probe called Explorer 1 into space. These first probes studied Earth from space. They also learned what it's like to be in space. This was the beginning of the Space Race between the United States and Soviet Union.