20 years of NASA's Mars exploration 0

Eight more NASA robots have explored Mars since Pathfinder became the first robot to land on the surface of the Red Planet on July 4, 1997 with the task of analyzing the atmosphere, climate and rock composition,

Pictured is the landing site of the Opportunity rover in 2004. Opportunity’s mission is to find signs of water on Mars.

Eight more NASA robots have explored Mars since Pathfinder became the first robot to land on the surface of the Red Planet on July 4, 1997 with the task of analyzing the atmosphere, climate and rock composition,

Pictured is the landing site of the Opportunity rover in 2004. Opportunity’s mission is to find signs of water on Mars.

20 years of NASA's Mars exploration

Sand dunes on the bottom of an ancient crater in the Noachis region, one of the oldest places on Mars.

Sand dunes on the bottom of an ancient crater in the Noachis region, one of the oldest places on Mars.

20 years of NASA's Mars exploration

Photo of molten sand dunes taken by the Mars Orbiter Observatory (MRO).

Photo of molten sand dunes taken by the Mars Orbiter Observatory (MRO).

20 years of NASA's Mars exploration

20 years since humans sent robots to explore Mars

Simulate the landing process of robots on Mars exploration.

20 years of NASA's Mars exploration

Winds with different directions and strengths create the diverse shapes of sand dunes on Mars.

Winds with different directions and strengths create the diverse shapes of sand dunes on Mars.

20 years of NASA's Mars exploration

The enchanting beauty of the sand dunes at Russell crater.

The enchanting beauty of the sand dunes at Russell crater.

Currents that may be caused by salt water are common on Mars during the warm months.

Currents that may be caused by salt water are common on Mars during the warm months.

The Opportunity rover operated for four months on the northern Greele Haven slope, taking over 800 images of the surrounding area.

The Opportunity rover operated for four months on the northern Greele Haven slope, taking over 800 images of the surrounding area.

A newly formed impact crater on Mars, about 30 meters in diameter, is located between large explosions.

A newly formed impact crater on Mars, about 30 meters in diameter, is located between large explosions.

At the north pole of Mars there are deposits of ground ice, three kilometers thick and about 1,000 kilometers in diameter.

At the north pole of Mars there are deposits of ground ice, three kilometers thick and about 1,000 kilometers in diameter.

The Curiosity rover is the most modern robot sent to Mars by NASA in August 2012 with 17 cameras, a laser device and a drill blade to find samples of rock powder formed in water.

The Curiosity rover is the most modern robot sent to Mars by NASA in August 2012 with 17 cameras, a laser device and a drill blade to find samples of rock powder formed in water.

Many areas on Mars have similar terrain features on Earth, such as river valleys, cliffs, glaciers and volcanoes.

Many areas on Mars have similar terrain features on Earth, such as river valleys, cliffs, glaciers and volcanoes.

NASA plans to launch the InSight mission in 2018 and send an additional rover in 2020 to continue studying Mars.

NASA plans to launch the InSight mission in 2018 and send an additional rover in 2020 to continue studying Mars.

A plume of late spring smoke on the surface of Mars.

A plume of late spring smoke on the surface of Mars.

Vu Phong (Photo: NASA)