The Curiosity rover mission team celebrates the landing of the car-size robot on the surface of Mars at NASA’s Jet Propulsion Laboratory in Pasadena, California on Sunday, Aug. 5, 2012.

On Aug. 5, 2012, NASA’s Curiosity rover touched down on the surfaceof Mars. Its mission: To find out if Mars could have once supported life. Nearly two years later, the car-size rover’s prime mission officially came to an end on Tuesday, June 24.

That doesn’t mean Curiosity will be put out to pasture. She’ll still be doing science on Mars and returning crucial data about the atmosphere and surface of the cold, red planet.

As the main investigation comes to a close, we spoke to chief scientist John Grotzinger, who has been directing the mission from NASA’s Jet Propulsion Laboratory in Pasadena, California. He talked about Curiosity’s biggest discoveries and one of the darkest moments during the mission.

[A lightly edited transcript of the interview follows]

Business Insider: How are you feeling now?

John Grotzinger: We feel really great about what we’ve been able to do. We’re hopeful that NASA will continue the mission. We are in the stretch of the fastest driving that we’ve done the entire mission so far. Now we’re trying to get toward Mount Sharp. We’ve had 16 papers published and two papers in Science magazine. We met all of the goals in advance. It doesn’t feel like mission over.

This is the first self-portrait Curiosity took after landing on Mars. It’s a bit fuzzy, but the pictures got better as the mission progressed.

BI: The last two Mars rovers, Spirit and Opportunity, also outlived their prime mission, by many, many years. Why is the main investigation so short if you know the machines can beat these expectations and how long do you expect Curiosity to last?

JG: NASA defines a set of objectives that the spacecraft is supposed to achieve within a timeframe, which was one Mars year or a little less than two years for Curiosity. The warranty on Curiosity expires in June, but we can see Curiosity’s vital signs working really well so we expect it to keep going. Curiosity is different than past rovers because it doesn’t have solar power, it has nuclear power. The way we generate power is that the radioactive device generates heat. There’s a device called the thermocouple, which converts heat to electricity. We can monitor its lifespan. We know we are going to get another good five years. After another seven years, we are going to be generating enough power to keep vehicle going, but not too much more. In 10 years, we expect to see significant degradation.

BI: What is the Curiosity team going to do now?

JG: A lot of team is now going to transition over to the Mars 2020mission. That’s the year it’s going to launch. I’m going to stick with Curiosity and make sure we make it to the base of Mount Sharp.

BI: How do you feel attached to Curiosity besides being the lead investigator?

JG: You can’t help but become emotionally attached to these robots even though they are mechanical devices. When something happens to Curiosity we not only feel the impact of the vehicle on Mars, but also on collective collaboration here. We watch everything she does. We watch the previous Mars rover, Opportunity, as she gets older and the same thing will eventually happen to Curiosity.

BI: Can you sum up the top three discoveries of the prime mission?

JG: The number one thing would be discovering evidence of habitability, meaning that we found an ancient environment where microorganisms could have lived and reproduced. If life ever evolved on Mars, this would have been place of it.

The second would be discovering and confirming something that had been guessed at in the 1970s: Mars lost a lot of its atmosphere billions of years ago. It became the planet it is today probably around 3 billion years ago.

Third, the place that we discovered that was habitable was younger than what we thought. What we though had been the “goldilocks window,” the time when the planet was habitable, was broader than what we thought before.

BI: Is there one day throughout the mission or challenge you faced that you would never want to relive again?

JG: Back in December, we had just published a series of papers that had proven the evidence of habitability early on. It even made the cover of Science. Two days later, I was alerted of pictures that showed thewheels had holes in them. The place we had landed in was very hazardous to the wheels. We got a flat on Mars. We developed a strategy to work around it and now are safely driving. But I would not want to go through that again. We had to stop driving when what we wanted to be doing was driving. We went from the greatest emotional high to the greatest emotion low in two days. It would have been nice to bask in glow of success a little longer.

The red circles highlight tears in one of Curiosity’s tires.

BI: In the first year of the mission you said something to a reporter about a discovery that Curiosity made, which got picked up by other media (including us) and somewhat blown out of proportion. What have you learned about the power of social media in this process?

JG: Social media is a wonderful thing. The overwhelming majority is so positive because the things you discover can be shared. We made the decision to return all images so people get to enjoy Mars the way they want. You do have to learn to be careful and explicit about what you mean.

BI: How soon do you think we’ll be able to put a person on Mars?

JG: The first thing we have to do is figure out how to bring rocks back. The difference between the moon and Mars is that the moon is a small body. With propulsion, it doesn’t take much energy to get off he surface. But Mars is big and it has gravity. You have to learn how to build a vehicle that can go to Mars, land successfully, and then lift off. But first we have to figure out the simple challenge of taking a 20 kilogram rock and lifting it off the surface of the planet.

BI: Do believe in programs like Mars One?

JG: In principle it’s possible.

BI: How are celebrating the end of the prime mission?

There’s going to be a big celebration on June 26. Engineers feel like they have delivered on their promise and built a vehicle that lasted a long time. Yes, there will be champagne.

Curiosity weighs about 1 ton and is around the size of SUV.

BI: Where is Curiosity going now?

We have 4 to 6 months of driving and are making great progress. We’re going to try to get to Mount Sharp by the end of the calendar year.

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