Since 1997, rovers on Mars have been exploring the riveting red planet eventually through an Exploration Program created by NASA. The first rover was the Sojourner, a 25-pound, 6-wheeled robotic explorer. Sojourner sent more than 550 pictures back to earth, which kept scientists busy for years. One of the more fascinating things that it found on the surface was pictures showing rounded pebbles and “conglomerate” rocks, indicating that there was something pushing different types of soil together at some point in the past. This was evidence of a more water-rich planet and indicated that the plain Sojourner was on may have been formed from floods.

Following Sojourners time in this intriguing place, there have been 3 other successful rovers to land on Mars: Spirit, Opportunity and Curiosity. They have all contributed to the expansion of our knowledge of Mars through findings, images, and other discoveries. Here are 7 of the most interesting discoveries that these rovers have found:

1. Spirit: discovered modern waters, or possibly frost, which had altered rock surfaces. There were complex coatings on olivine basalts to prove this. This was found on the Gustev Crater.

2. Curiosity: measured the radiation on Mars. This is interesting because it can help inform the hazards if human visitors were sent to the planet. The radiation levels are comparable to those experienced by astronauts the International Space Station.

3. Opportunity: discovered wind-blown ripples. These were found on the Meridiani plains and are indicators of a previous wind regime, probably when Mars’ spin axis tilt was different than it is today.

4. Spirit & Opportunity: discovered Dust Devils. These show how sand and dust are moved by the wind in Mars’ very thin atmosphere.

5. Opportunity: prior habitable environment. Opportunity found evidence through clays and formation rocks that suggests Mars may have been habitable for millions of years. These rocks were the oldest rocks examined by the rover, about 4 billion years old.

6. Curiosity: possibility of previous life (cont’d). Thanks to Curiosity, scientists found more evidence that Mars likely had the chemistry to support living microbes. Curiosity drilled into Martian rocks and discovered carbon, hydrogen, oxygen, phosphorus, and sulfur–all of which are the “key ingredients” to life.

7. Curiosity: significant geological diversity. Curiosity found different types of gravel, streambed deposits, possible volcanic rock, sand dunes, mudstones, and cracks filled with mineral veins. This variety of sand and rock found in the Gale Crater surprised Scientists.

Opportunity has been going strong on Mars for over 10 years now, even though its twin, Spirit, was declared dead in 2011. Curiosity is still on the Red Planet as well, gathering new information and making new discoveries daily. Within the past 18 years, so much information and evidence has been gathered about this planet. I am interested to see what comes of it in the future, and if habitability will ever be an option again.