Amitabha Ghosh , Chairman, Science Operations Working Group -- Mission Operations at the NASA Mars Exploration Rover Mission, has worked on Vesta -- an asteroid whose geological processes uncannily resemble those of Earth's -- and several generations of Mars missions, starting with the Pathfinder in 1997 and most recently, the Curiosity Rover. The NASA geologist speaks to ET in San Francisco about Mars, the future of space explorations out of India and the US, the debate over manned missions and about his Indian roots. Edited excerpts:

What's next after the Curiosity mission? Where will it eventually lead us to?

Can life survive on Mars? That's what we want to know. Water sustains life on Earth. And this decade, we have already verified the presence of water on Mars. Life on Earth is made of carbon and all life is made of organic compounds. This mission will verify if there are organic compounds on Mars or not. If there are, then the next step would be a biological mission to determine whether this Martian organic compound is animate or not.

What are the technical and financial challenges facing expensive government missions?

Whenever you go to another planet, you have to take into account engineering constraints, which are enormous and vary from case to case. For instance, where do you deliver the spacecraft? Suppose if Curiosity had landed on a rocky bed with boulders, it could have toppled: there could have been inherent risks to the spacecraft. Then there are atmospheric constraints like what is the atmospheric speeds. The landing site is chosen on many such parameters.

When it comes to sending humans to Mars though, it's not a technology issue. We have the technology. What we don't have is the money. Sure there's tremendous national pride. But can any country spend a trillion dollars to send its people to Mars? Even if we weren't in an economic recession, it's a hell lot of money!

What then is the long-term future of space explorations?

Any frontier explodes only when there is a commercial reason to do it. Look at the Internet: when it happened in a lab, nobody cared. But when cloud computing came up, it exploded.

The fundamental cost of getting out of orbit is enormous! And while a private company like SpaceX might take care of some parts, we are at a stage when we need to make a plausible business case to a venture capitalist. For instance, there are diamonds in space and so I'll go and get it. Therefore, the Google Lunar X Prize model, while commendable, might not be a valid business model. There isn't a compelling financial case for it. Even if you look at SpaceX, who is the primary customer? It's the government, which is certainly not a very good place to be at.

And if you look at startups wanting to fetch moon rocks, it's a niche market. Diamonds aren't that rare but De Beers sold a campaign, "A diamond is forever". Will a rich trader from China or India want to give a moon rock to their wife or girlfriend and pay a ton of money for it? Does the market want what you're bringing? Space exploration is yet to build a market and a fundamental business case and I'm afraid we aren't there yet.

Another huge thing is the advent of robotic space exploration. We have just sent three generations of rovers to Mars. Not only is it cheaper it's a lot easier than a human mission. And we will see a lot more countries get into it. You don't have to support life systems. You also forgo huge technical and financial challenges of the launch factor involved in a human mission: you have to launch from the gravity of not just your own planet, but also the other planet, because you have to bring these humans back to Earth.

If there was a specific economic reason it might still be possible. For instance, we can get iron ore and other geological resources (that we could run out of on Earth in 65 years or so) from other planets and asteroids. At some point, there will be a major geological resource scarcity. But even then, will we be able to justify the cost of a human mission? After all, we use robots for anything that's dangerous, dull or dirty. And this is dangerous. So, why take the risk of sending humans when robots can do the job better and cheaper? The only case for a human mission would be public fascination.

What about NASA? Are its golden days truly over, as believed?

First, it's not true that budget cuts have crippled NASA. Budget cuts have happened across all US government agencies and NASA can still deliver on tough projects. For some reason s-- perhaps a fascination for space -- the best people still come to work for NASA. So, unless the budget cuts get really drastic, NASA will do innovative projects. It already has a very aggressive portfolio of missions like a Mars Orbitter planned in 2013, and missions to Vesta and Pluto. Not all space agencies are as successful in attracting talent as NASA. And as long as it can, it will do just fine.

How does this compare with India's own space programme?

India is at a very interesting crossroads in space. Space is bipartisan. Everybody supports it, the BJP, the Congress, the public. Nobody is opposed to it. Chandrayaan was almost a matter of national pride. It's similar to the US space scene in the 1960s and the 1970s. ISRO's budget too has gone by almost seven times in the last few decades. And India has the public and political mandate to move ahead. But it does not yet have the technology heritage; this is something it has to build. For instance, it is nowhere near sending a human to space like say, China which is much ahead and has already sent a human to space.

The only caveat is that people in India need to understand that there will be frequent failures and you should be able to move ahead and go on in spite of them. Space -- and especially Mars, which India seems to be planning for -- is after all a risky business and everybody, including NASA have had very public failures.