I think the next major step will be the discovery of life on Mars or somewhere else in the solar system, past or present day, which would stimulate exploration to find out more about it.
ExoMars in 2018 will be first to look for life directly on Mars. Our other rovers sent to Mars so far (with possible exception of the Viking labelled release) would not spot life in the Atacama desert or the McMurdo dry valleys and unlikely to spot life on Mars past or present.
That's because past life is so deteriorated by cosmic radiation if on the surface and by radiation of the rocks below the surface - and for present day life - Mars is basically in a "Snowball Mars" phase at present - a "dry snowball" - so little water that it isn't white - but if it had water it would be white from poles to equator. It would be hard to spot life on Earth during its snowball phases in the past - and even harder to spot life on present day Mars.
All the possibilities are exciting and could revolutionize life sciences. If Mars has never had life - then that's puzzling because of the amount of material exchanged with Earth and the habitability of past Mars - and it could tell us much about whether life is common in our universe - or rare - and what happens to a planet which is habitable and left for some hundreds of millions of years and doesn't evolve life - what does happen in that case instead of life? Protobionts for sure as they happen in the laboratory - cell like structures that aren't quite living.
The least interesting possibility is if Mars has present day and past life that is identical to Earth life in all respects. Robert Zubrin and a few others have made this as a hypothesis. But - is hard to see how it could happen as only a few extremophiles could make the transfer between the planets - and not been proved that any of those do it either - and if they did - last chance to go from Earth to Mars was probably tens of millions of years ago - and if it did happen - the extremophiles could co-exist with native Mars life, could exchange gene fragments with them if the biochemistry is compatible - and would surely evolve away from their Earth cousins in the very different Mars climates.
So - I expect that to be the interesting discovery of the next two or three decades, at some point we will either discover life on Mars - or discover ancient organics without any life and present day habitats without any life in them. And - both possibilities would be fascinating.
Then - as for humans - the time of EVAs may be over, because it's so hazardous for a human in an unprotected spacesuit, if you want to spend days and years in space conditions. Instead we may soon start to use telerobotics for almost all space operations - operated by humans inside the spacecraft - or on the Moon - or on the Earth if close enough to do that.
We may also see more and more use of autonomous robots - robots far more capable than Curiosity, able to make their own decisions and travel around on distant objects in the solar system at the speeds of the lunar rover and faster, and pick things up and analyse them and make decisions about where to go autonomously with only occasional instructions from Earth.
Hard to tell which of those will come first.
Also develop artificial gravity and better closed system habitats - and cosmic radiation shielding - once that is possible - then exploratory missions with humans on board could survive for years on end anywhere in the solar system without supply from Earth.
So for humans - next step I think - to find a way to survive in space without supply from Earth - and to test it with long missions e.g. to the L2 position on far side of the Moon for telerobotic exploration of the far side of the Moon - or missions to the lunar surface.
Then a bit later on human missions to explore further afield via telerobotics once we have shown that humans can survive for years on end in space conditions.
For robots - more and more autonomous missions. Also increasing use of micro-sats and tiny interplanetary spacecraft - tiny cm scale robots sent to distant parts of the solar system. Including clusters of microbots communicating with each other e.g. to explore caves on Mars.
And development of better telerobots able to co-operate with humans and be controlled, with binocular vision, haptic feedback, able to move anywhere in response to a human walking on an omnidirectional treadmill such as the Virtuix Omni etc. So then a human safely protected in a spacecraft orbiting a planet can walk around on the surface and experience it even better than they could if they were on the surface encumbered with a clumsy spacesuit. This I think could become the norm as soon as a couple of decades from now - and we could already start telerobotic exploration with present day technology - has been proposed for exploring both Mars and the Moon and I think if humans return to the Moon - or travel to Mars orbit - with present day technology - even right now, they will use telerobots extensively (would be a major missed opportunity if they don't).
ExoMars in 2018 will be first to look for life directly on Mars. Our other rovers sent to Mars so far (with possible exception of the Viking labelled release) would not spot life in the Atacama desert or the McMurdo dry valleys and unlikely to spot life on Mars past or present.
That's because past life is so deteriorated by cosmic radiation if on the surface and by radiation of the rocks below the surface - and for present day life - Mars is basically in a "Snowball Mars" phase at present - a "dry snowball" - so little water that it isn't white - but if it had water it would be white from poles to equator. It would be hard to spot life on Earth during its snowball phases in the past - and even harder to spot life on present day Mars.
All the possibilities are exciting and could revolutionize life sciences. If Mars has never had life - then that's puzzling because of the amount of material exchanged with Earth and the habitability of past Mars - and it could tell us much about whether life is common in our universe - or rare - and what happens to a planet which is habitable and left for some hundreds of millions of years and doesn't evolve life - what does happen in that case instead of life? Protobionts for sure as they happen in the laboratory - cell like structures that aren't quite living.
The least interesting possibility is if Mars has present day and past life that is identical to Earth life in all respects. Robert Zubrin and a few others have made this as a hypothesis. But - is hard to see how it could happen as only a few extremophiles could make the transfer between the planets - and not been proved that any of those do it either - and if they did - last chance to go from Earth to Mars was probably tens of millions of years ago - and if it did happen - the extremophiles could co-exist with native Mars life, could exchange gene fragments with them if the biochemistry is compatible - and would surely evolve away from their Earth cousins in the very different Mars climates.
So - I expect that to be the interesting discovery of the next two or three decades, at some point we will either discover life on Mars - or discover ancient organics without any life and present day habitats without any life in them. And - both possibilities would be fascinating.
Then - as for humans - the time of EVAs may be over, because it's so hazardous for a human in an unprotected spacesuit, if you want to spend days and years in space conditions. Instead we may soon start to use telerobotics for almost all space operations - operated by humans inside the spacecraft - or on the Moon - or on the Earth if close enough to do that.
We may also see more and more use of autonomous robots - robots far more capable than Curiosity, able to make their own decisions and travel around on distant objects in the solar system at the speeds of the lunar rover and faster, and pick things up and analyse them and make decisions about where to go autonomously with only occasional instructions from Earth.
Hard to tell which of those will come first.
Also develop artificial gravity and better closed system habitats - and cosmic radiation shielding - once that is possible - then exploratory missions with humans on board could survive for years on end anywhere in the solar system without supply from Earth.
So for humans - next step I think - to find a way to survive in space without supply from Earth - and to test it with long missions e.g. to the L2 position on far side of the Moon for telerobotic exploration of the far side of the Moon - or missions to the lunar surface.
Then a bit later on human missions to explore further afield via telerobotics once we have shown that humans can survive for years on end in space conditions.
For robots - more and more autonomous missions. Also increasing use of micro-sats and tiny interplanetary spacecraft - tiny cm scale robots sent to distant parts of the solar system. Including clusters of microbots communicating with each other e.g. to explore caves on Mars.
And development of better telerobots able to co-operate with humans and be controlled, with binocular vision, haptic feedback, able to move anywhere in response to a human walking on an omnidirectional treadmill such as the Virtuix Omni etc. So then a human safely protected in a spacecraft orbiting a planet can walk around on the surface and experience it even better than they could if they were on the surface encumbered with a clumsy spacesuit. This I think could become the norm as soon as a couple of decades from now - and we could already start telerobotic exploration with present day technology - has been proposed for exploring both Mars and the Moon and I think if humans return to the Moon - or travel to Mars orbit - with present day technology - even right now, they will use telerobots extensively (would be a major missed opportunity if they don't).
About the Author
Robert Walker
Writer of articles on Mars and Space issues - Software Developer of Tune Smithy, Bounce Metronome etc.Studied at Wolfson College, Oxford
Lives in Isle of Mull
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