Introduction

The U.S.-Russian space race is beginning to lose steam. As spacecraft become more reliable, scientists and engineers plan increasingly distant and difficult tasks - developing more sophisticated robotic explorers and instruments that will enable robotic explorers to land on the surface of Venus and Mars and travel to the outer planets.

The ratio of success increases dramatically in the 1970s. Of the 45 interplanetary spacecraft launched in this decade, 31 completed their missions, three were partial successes and 11 were lost.

September 12-21, 1970

Russia collects its own Moon samples. The Luna 16 spacecraft collects 105 grams (about a quarter pound) of lunar soil, deposits them in a container and launches them back to Earth - the world's first - and still one of the few - robotic sample returns.

November 17, 1970

A precursor to modern robotic rovers, Russia's Lunokhod 1 makes history as the first unmanned wheeled vehicle on another world. Weighing in at a hefty 900 kg (2,000 pounds), Lunokhod 1 explored the Moon for an incredible 322 Earth days before sending its final signal on Sept. 14, 1971.

Lunokhod 1 (part of the Luna 17 mission) is considered one of the greatest successes of Russia's lunar exploration program.

December 15, 1970

Russia becomes the first nation to receive signals from another planet as the Venera 7 lander sends back data from the surface of Venus for 22 minutes and 58 seconds. The spacecraft was most likely then overcome by Venus' intense heat and surface pressure.

Venera 7 was launched on Aug. 17, 1970.

November 14, 1971

After a journey of more than six months, NASA's Mariner 9 spacraft enters orbit at Mars - becoming the first human-made object to enter orbit around another planet. The spacecraft mapped about 85 percent of the planet at a resolution of 1 to 2 kilometers and identified more than 20 volcanoes, including Olympus Mons, the largest volcano in our solar system.

Mariner 9 was last contacted on Oct. 27, 1972.

November 27, 1971

Russia's Mars 2 is the first probe to the surface of Mars. A computer error brought the lander in too steep and it smashed into the surface, but it is still the first human-made object to touch the surface of Mars.

July 1972 - February 1973

NASA's Pioneer 10 is the first spacecraft to cross the main asteroid belt between Mars and Jupiter.

December 4, 1973

Pioneer 10 is the first human-made object to reach Jupiter, our solar system's largest planet. The mission is NASA's first to the outer planets. Pioneer 10 took about 300 photos of Jupiter.

Jupiter's powerful gravity propels Pioneer 10 on a course to Saturn and eventually into interstellar space. Both Pioneers 10 and 11 carry a plaque containing information about the human race and its location in our solar system.

February 5, 1974

NASA's Mercury-bound Mariner 10 makes the first use of another planet's gravity to change its trajectory as it passes by Venus. Gravity-assist is another key step in solar system exploration. It saves fuel - a precious commodity on a weight conscious spacecraft - and will ultimately open up the outer solar system to exploration.

Mariner 10 also took more than 4,100 images as it flew past Venus.

March 29, 1974

NASA's Mariner 10 logs another first as it flies by Mercury in the first of three passes. The spacecraft took the only close-up images of Mercury, revealing a battered, Moon-like surface dominated by craters. It also confirmed that Mercury had no atmosphere.

Contact was lost on Mar. 24, 1975. Mariner 10 will be the last spacecraft to visit Mercury for more than three decades.

October 22, 1975

Humans see the first grainy black-and-white pictures from the surface of another planet as Russia's Venera 9 sends back images from the surface Venus. Cloaked in toxic clouds and scorched by the hottest surface temperatures in our solar system, the landscape of Venus remains a mysterious. The Venera 9 orbiter is the first spacecraft to orbit Venus.

The lander sent back 53 minutes of information from Venus' superheated surface.

July 20, 1976

NASA's Viking 1 lander is the first spacecraft to touch down safely on Mars. It sends back the first pictures and studied the first soil samples from the surface of the Red Planet.

The lander sent back regular weather reports from Mars until contact was lost on Feb. 1, 1983.

September 1, 1979

NASA's Pioneer 11 is the first spacecraft to reach Saturn before continuing on a course that will ultimately take it out of our solar system.