Laurie Leshin is a scientist who studies the formation and evolution of the Solar System.
Now she advises on the US presidential commission that will direct a space exploration programme to go to the Moon and then on to Mars.
Leshin: Mars can help us answer some profound questions
She told us why we need to send people to the Red Planet.
Why is sending humans to Mars so important?
Mars is a place that holds special promise in terms of being able to answer whether or not we are alone in the Universe. I think we require human presence to be able to make real time decisions and go off in new directions if the rocks warrant it.
We also need to access the places on Mars that are most interesting - like liquid water environments. We can't see those at the surface today. They might be down deep and astronauts can drill. You can't do that robotically.
Do you think we have been bogged down in a low-Earth orbit for the last 40 years?
Robots just can't answer all the questions... humans have the ability to respond and react to information in ways that robots don't
We are only a couple of hundred miles up with the space shuttle. We are not even sending humans the length across the state of Arizona. A couple of hundred miles up is not very far to go. We have a lot to learn again about how to go out beyond low-Earth orbit and that is really why the Moon is so important.
We need to learn how to have spacesuits that work in deep space and closed-loop environmental systems that last a long time on the surfaces of other planets. There are just whole new challenges in exploring other planets.
We have a fantastic array of probes on Mars. What can humans do that they can't?
Robots just can't answer all the questions. They can do amazing things as we've seen with Spirit and Opportunity. But humans have the ability to respond and react to information in ways that robots don't.
In addition, all the tools that we will send with humans are just going to make us so much more capable on the surface of making discoveries.
You can imagine how Opportunity has been running around at this beautiful rock outcrop on the surface of Mars. An astronaut up there would have paced that place out and had it understood within a day and we've waited a month-and-a-half.
So just the pace of discovery and the kind of depth of understanding that we will need to understand whether life got started on Mars, I think is really going to take human eyes to figure out.
But sending humans offers such challenges doesn't it? What about bone density loss and muscle wastage?
There are many challenges in this exploration endeavour. Two important ones are the human factors and the technological challenges to get humans to Mars.
Both are important and it's not get clear which are going to be the tallest tentpoles - as we like to say - in getting us there. So both of those things are high up on our radar screen of things we need to look at more.
The idea is to go in a generation's time. How are you going to protect the funding and keep that vision alive?
Astronauts will need to stay fit and healthy on the long mission to Mars
It's a real challenge to build up consensus, to keep an exploration project like this going. In fact, the money is not much more than Nasa is getting now. So in that sense it's not as great a challenge as you might think.
But Nasa without a direction is even harder to sustain than Nasa with a wonderful vision and direction. So now we've got that, it's just up to us to take advantage of it and make it work.
The programme has to survive several presidents. How will you cope with that?
There are challenges - absolutely. And I always come back to this idea that we have to explore because that's what being a prosperous culture is all about. It's about educating the youth of tomorrow with the excitement of today and encouraging those kids to go into science and maths so they can fill the jobs of the future.
They are the people that are going to be the architects of our futures. That's one component. There's a political component and there's a private industry component and a government component. And we are working on all of those things to make this happen.
Would you like to send a sample return mission before we send people to Mars?
Nasa without a direction is even harder to sustain than Nasa with a wonderful vision and direction. So now we've got that, it's just up to us to take advantage of it and make it work
Well, there are a lot of things we need to know about Mars before we can send humans. We need to understand better what the surface is really made of. Are there hazards? What's all this dust? Is it going to get in everything?
To do those things to a level that will really let us design a manned Mars mission I am convinced we really need to bring those materials back. So that's got to be one of the missions that leads up to sending humans.
Plus, we'd like to demonstrate the capability to go to Mars and come back robotically before we send humans.
What is your hope for 20 to 30 years' time?
Well the hope I have is to some day be at the 25th anniversary of the first human mission to Mars. I'd like to have the first astronaut that went there and walked on the surface, stand up, talk about her experience and say: "I was inspired when I was a kid after seeing little rocks from Mars in the Smithsonian and that's what made me want to go.
And if I could be involved with bringing those materials back and inspiring the person that is going to be that first Mars astronaut, it would just be extraordinarily exciting. I'd be happy to be an old lady seeing that.