By Dr David Whitehouse BBC News Online science editor

Although the discovery of vast ice reserves brings forward the prospect of a manned landing on Mars, the American space agency (Nasa) is in no hurry to embark on a formal effort.

The agency will certainly not make any such commitment this week when the latest study results from the Mars Odyssey probe are officially published in Science magazine.

If the crew is relying on technology to manufacture its rocket fuel to get home from the hydrogen and oxygen locked up in the Martian ice then it had better work - first time

But the idea of a manned mission to the Red Planet is always there as the unstated climax to a series of ever more sophisticated robotic missions - probes that will roam across the Martian surface and bring back rocks to Earth for analysis.

For many, the promise of the Red Planet, and our generation's place in history, is only partially fulfilled if we do not eventually send people to Mars.

When and how are secondary issues. Somehow, there is something deep within our nature that will be unsatisfied if we just let the robots do it all.

Political will

Be assured, a manned mission will take time to devise and execute - something like 20 years in the current climate. That means the first person to walk on Mars is probably currently in his or her teens.

It would be a mission that lasted several years

The US went to the Moon for politics and then abandoned the satellite because the case for staying did not sway the politicians. There is no Mars race between superpowers in the offing, so going to the Red Planet will be for other reasons, and will take longer.

But then, hopefully, the commitment will also last longer than for the moonshots.

Getting to Mars will certainly be much more difficult. The Moon is only three days away; Mars is 300.

A round trip will take two and a half to three years and require a substantial stay on the Martian surface.

Return ticket

Recycling will be a major issue. A spacecraft cannot possibly carry all the food and water it needs for a crew of several. Our current recycling technology is good - but not good enough.

Mars facts

Equatorial diameter - 6,791km Martian day - 24 hours, 37 minutes, 23 seconds Martian year - 687 days Mars-Sun distance - 227.7m km Moons - Phobos and Deimos

No humans will have ever been so far away from Earth as the first Mars crew. How will that affect them psychologically? How will they get along with each other cooped up in such a small space for a year?

The crew will have to be specially selected to be able to cope. Should it be a mixed crew or all men, or all women?

And what of the technologies these emissaries will need to use when they land on Mars?

Knowing that vast swathes of water-ice just below the surface are there is one thing - being able to dig it up and turn it into fit drinking water or rocket fuel is another matter altogether.

All people

And remember, there will be no second chances on Mars. If the crew is relying on technology to manufacture its rocket fuel to get home from the hydrogen and oxygen locked up in the Martian ice then it had better work - first time.

One question intrigues me: who should put the first human footprint on Mars?

Should it be an American - as surely only the US will be in a position to mount such a mission for a long time to come?

One appealing suggestion I heard a few years ago is that included in any crew should be a representative of the poorest nation on Earth and that this individual should make the first footfall on another world as a pledge to the poor of planet Earth.

And if this person did become the first human to stand on the red soil of Mars, what would they say? Discuss.

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Your views:

We already have the technology for a mission to Mars. I would volunteer to go if someone was to send a mission - even if it's one-way, it's an opportunity of a lifetime! Where would mankind be today had we not taken any risks in the past?
Will Metcalf, UK

I want big green aliens with tentacles

Peter Hope, Ireland

I'm bored of these lame galactic discoveries. I want to see big green aliens with tentacles like in the movies and not some little micro thingies fossilised in a rock. Discovering water is completely boring too. I think it's about time NASA start showing the goods.
Peter Hope, Ireland

Instead of circling the Earth, the International Space Station should be put into an orbit between Earth and Mars. This could then be used to carry explorers on unlimited journeys to and from Mars, and actually make the vast expense worthwhile.
Mal Lansell, England

It's sexy, exciting and the stuff of dreams - but how, with nations lining up to annihilate each other with weapons of mass destruction, millions dying from famine, drought, disease, slavery, oppression and global warming - can we justify spending the hundreds of billions of dollars it would take just to put one or two lucky individuals on Mars' surface? We should be confronting and solving our problems in the here and now, not looking for ways for a handful of the "great and good" to run away from them.
Steve Pauline, UK

Why has humankind lost the explorer urge?

James C Becknell, US

Why has humankind lost the explorer urge? It has been over 30 years since we landed on the moon. In that same span of time after Columbus, major colonisation was underway in the New World. It was relatively a far more difficult task.
James C Becknell, US

What makes this discovery most interesting is the possibility of life. Many people would feel threatened with sharing this universe with strangers. Let's just hope that if that does happen, if they do find life, humans will not move towards what seems to be their instinctive desire to murder and dissect.
Semira, Canada

Wonderful; one of the most important discoveries ever made. With water found at our closest planet, the probability that life exists elsewhere in our galaxy increases immeasurably.
John S. Chilton,

I couldn't care less if there was once life on Mars

Craig Grannell, Iceland

It amazes me that so much money is being spent on searching for alien beings when we are gradually killing off the genuine alien intelligences on our own planet. I couldn't care less if there was once life on Mars, or if it's still there.
Craig Grannell, Iceland

I don't think bringing samples back is a good idea. What about the risk of deadly Martian bacteria which grow slowly on Mars, but which, on entering the Earth's atmosphere, grow incredibly quickly, and wipe out the entire world population? Maybe I've seen too many Martian movies?
Jon, UK

It's nice to see that there is even more water than we had dared hope for. I think I'd now be suppressed if evidence of live did not come to light. However, the idea of NASA launching a manned mission within twenty years is currently laughable. Look how bad they are at managing the ISS. NASA also don't seem to admit that to be remotely safe, a Mars mission will require double or triple redundancy of all aspects of it. This has never been factored into the more optimistic cost projections - it will cost probably around a trillion dollars when we finally do go.
Jim Moores, UK

I'd be interested to hear what the Vatican would have to say

Bubble/Slide, UK

I'd be interested to hear what institutions such as the Vatican would have to say if life were to be discovered off this planet.
Bubble/Slide, UK

I say great. Let's go and colonise Mars. The property prices are bound to be cheaper than London.
Richard, UK

Amazing news! But I think humans shouldn't land on Mars at all. They could destroy a life-form by their mere presence on the planet and destroy any future prospects for any existing life there evolving into higher forms or even intelligent life. I am thinking here in terms of an evolutionary time scale. Monitor but do not enter should be the order of millions of years to come.
Frank Schumann, Germany

Mars was the origin of all life on Earth

Roy, US

I believe that Mars was the origin of all life on Earth. It was inhabited but when water became scarce millions of years ago the inhabitants left and came here.
Roy, US

It shows that if you look long enough and believe hard enough you can prove anything.
Natasha Britt, England

I fail to see why this is such an exciting discovery. Mars is freezing cold with a thin atmosphere and not much use for anything, and now we discover it has a polar ice cap...mmm not exactly Bermuda!
Tom, UK

Another small step on the journey to the stars but, "Sometimes I think the surest sign that intelligent life exists elsewhere in the Universe is that none of it has tried to contact us."
(Calvin).
Frank McClintock, Portugal

Quick! Let's go there, refuse to come back and claim Mars as a sovereign state. The Welsh Republic of Mars. I'll be president!
Elwyn ap Bernard, Wales

Mars is too far from the sun and too cold

Jonathan Fish, France

Unfortunately, the discovery of ice on Mars does not make life on Mars past or present very likely. Mars is too far from the sun and too cold for self-reproducing molecular systems to have ever evolved there. Any imaginable life-like chemistry would need liquid water and surface temperatures well above zero degrees for complex carbon compounds to react and evolve. After all any Martian looking at earth would say that life on Earth is impossible.
Jonathan Fish, France