Robots vs. Humans: Should we cede solar system exploration to the robots? Do humans have a place beyond low Earth orbit?

By Dr. Cynthia Phillips
Planetary geologist at the Carl Sagan Center for the Study of Life in the Universe, SETI Institute

The final mission of Space Shuttle Atlantis has spawned a whole series of perspective pieces on the history, state, and future of space exploration. Some, like the YouTube video "NASA's increase of awesome to continue," are unabashedly exuberant celebrations of the future in store for us in space; others, like this thoughtful piece in Technology Review entitled "Was the Space Shuttle a Mistake?," are depressingly and effectively critical of the cost both in dollars (more than $200 billion) and in human lives lost (14 astronauts plus at least 6 ground support staff) of the Shuttle program. Some authors have even posited the end of the space age altogether, as in a piece subtitled "Inner space is useful. Outer space is history" in The Economist.

While some of these articles make throwaway references to the number of robotic missions that could have been launched for the cost of one Shuttle flight (estimates range from $450 million per launch, one Discovery-class mission, up to $1.6 billion per launch, half a Flagship mission), there has been little analysis to date of the relative merits of human exploration vs. robotic exploration.

As a planetary scientist, I have very mixed feelings about the human spaceflight program. On a purely scientific level, there is very little in our current solar system exploration program that can't be done just as effectively by a robot as by an astronaut. Robots excel at the tedious work of taking similar pictures or analyzing similar rocks over and over and over again, without complaint (usually!) or a need for life support systems. Robots don't need food or water, they can withstand much more damaging radiation, and, perhaps most importantly, they don't need to come home at the end of the mission. Simply put, a one-way trip requires only half the fuel of a round trip voyage, and even though you'd likely get plenty of volunteer astronauts signing up for a one-way trip to Mars, it's unlikely that our current moral and ethical code would allow us to send such a mission.

And yet. While orbiting robotic probes have taken stunning vistas of the outer Solar System, it is clearly our rover missions on Mars that have won the hearts and minds of the general public. Perhaps it is the anthropomorphic, almost cute appearance of Spirit and Opportunity (and don't underestimate the cuteness factor), but I think it's also that rover tracks are the closest thing we currently have to astronaut footprints on the surface of another world.

If you think of an iconic image of space exploration, chances are you'll come up with an astronaut planting a flag on the Moon, or perhaps that classic image of a single bootprint from Apollo 11. Robots have flown past, orbited, and/or landed on all of the major bodies in our solar system and quite a few of the minor bodies -- we've landed spacecraft not only on Mars, but also on Venus, the Moon (of course), and Saturn's moon Titan; we sent an atmospheric probe into Jupiter; we're currently in orbit around Mercury and Saturn; and we've flown past Neptune and Uranus (and are on our way for a flyby of that pesky has-been, Pluto). Yet without that bootprint, that iconic image of "touching the surface," have we really explored those worlds?

Ironically, if the next target of human space exploration remains a trip to a near Earth asteroid, the "boots and flag" doctrine becomes extremely complicated in an irregular microgravity environment. If an astronaut visits an asteroid, she probably won't actually be able to stand on it because there won't be enough gravity. Landing would be extremely difficult, but perhaps a spacecraft could rendezvous with an asteroid by matching its speed and let an astronaut drift over to pay a visit to a large space rock. Rather than trying to make a bootprint on the surface, wouldn't a large pole be easier for her to poke the surface with? It could even collect a sample while making a boot-shaped impression. But then do we need the astronaut outside in her suit in the dangers of space after all? Couldn't she just operate the pole with a boot on the end from safely inside her spacecraft? What if she operated it remotely, from a larger spacecraft perched a safe distance away from the asteroid? What if she stayed home and operated it truly remotely, from the comfort of a safe NASA facility's virtual reality tank? What if the boot-and-pole contraption didn't need to wait for signals from a faraway human astronaut at all, but could be programmed to autonomously tap the surface on approach, make and photograph a nice boot-shaped mark, and perhaps even scoop up a sample or two of asteroid dust to send back to Earth in a small capsule? Would that allow us to check off "asteroid exploration" from our list? What if I told you that mission has already been accomplished -- the Japanese Hayabusa spacecraft successfully used a robotic probe to capture a small sample of dust from the asteroid Itokawa in 2005, placed it in a capsule, and sent it back to Earth, where it was successfully recovered in 2010 and is currently being studied.

But what about the science, you say, all that science that can only be done by trained astronauts? What about the amazing green moon rocks that were found by the Apollo astronauts on the lunar surface but surely would have been missed by a robot? To this, I would argue that while certainly human astronauts have the benefit of intelligence, quick thinking, problem solving, and ingenuity, robots have certain inexorable advantages in the realm of space exploration. Aside from not needing to eat, sleep, or return to Earth, robotic missions are significantly cheaper than human missions. For the cost of putting two astronauts on the surface of a planet like Mars for a few days or weeks, you could afford an army of robots that could comb the surface of the planet for years. While they might not spot that green rock right away, through sheer brute force chances are they'd eventually stumble across it and catalog it as an interesting sample to be sent back to Earth someday. And if you don't have humans to return to Earth (and keep alive and safe all the way home), you have room for a whole lot more rocks in your return capsule!

So why, then, do I have mixed feelings about the end of the Space Shuttle program? If everything humans can do in space, robots can do better, cheaper, and safer (in terms of loss of human life), then why send humans at all? The answer is simple: don't try to justify human spaceflight using science. NASA got it right when it split off the Science Mission Directorate (SMD) from the Exploration Systems Mission Directorate (ESMD). Keep exploration, dominated by human astronauts, separate from science, where robots rule. Sure, there may be some chances for science to be done along the way, as in the interesting geological observations made by the Apollo astronauts or the microgravity chemistry experiments performed by astronauts on the International Space Station, but if you try to justify a program like Apollo or the ISS purely on scientific terms, you'll fail. For the $25 billion spent on the Apollo program (a more inclusive estimate in 2009 dollars is $170 billion), or the $100 billion spent on the International Space Station (which includes construction costs plus the cost of 33 Space Shuttle missions to construct and supply the station), we could have had a small army of robotic lunar geology rovers or a fleet of microgravity satellites. Apollo and the ISS belong firmly in the Exploration side of NASA's portfolio, and that's as it should be.

Why, then, should we explore at all, if not for scientific gain? As a scientist, this might be a hard position to admit, but exploration has political and psychological benefits that go far beyond science in many respects. The Apollo program was a unique circumstance of the Cold War era -- instead of fighting a war on the ground, with potentially devastating consequences from the use of atomic or nuclear weapons, the United States and the Soviet Union chose astronauts and cosmonauts to fight in a modern-day arena: space became the gladiator ring of the past. In a post-Cold War era, the International Space Station became a sign of international cooperation and trust, as governments from many countries shared resources to build and staff a technological marvel in orbit.

Human spaceflight gives us a new perspective on our world, fragile and beautiful in an endless, empty sea of darkness. It is inspirational, a source of pride in our nation's accomplishments, a uniting subject at a time of great national divisions. And it is space travel that lights up the minds of children, of the next generation of explorers, sparking a seed of innovation and excitement and exploration that will carry this nation forward. NASA should be on the cutting edge of that exploration.

The Space Shuttle was an innovative technological marvel in 1981, when it was first launched, but it has kept flying far longer than originally intended, and the fleet of spacecraft has grown old and unreliable. Many things have changed since 1981, and it's time for a change in our human spaceflight policy, as well. I believe that the Obama administration made a tough but correct decision when it decided to encourage commercial development of spacecraft that can serve as the cargo ships and true "space shuttles" of the future, bringing supplies and astronauts to the International Space Station and other future destinations in Low Earth Orbit. Atlantis' final journey into space turned out to be both majestic and mundane, as the science fiction spacecraft of the future (at least the future as seen in 1981) ends its days ferrying a load of spare parts and bologna sandwiches into orbit and bringing a load of broken equipment and assorted trash back to Earth. Such resupply missions are clearly better suited to the shipping containers of the future, robotic resupply ships that are already automatically docking with the ISS which are unloaded, then filled up with trash and released to burn up in the Earth's atmosphere on the way down.

NASA's future of human spaceflight will focus on innovation and true exploration, not the day-to-day operations of the supply chain. As Space Shuttle flights became ordinary, they lost their place in the human imagination because they ceased to be exploration - while the scenery is stunning, there are only so many times that a trip around Earth or a visit to the same Space Station can be spun as new and exciting on the evening news. A focus on developing flexible, innovative, and realistic new spacecraft that can take astronauts to Near Earth asteroids (with or without a boot-on-a-pole), or back to the Moon, or even on to Mars, will give NASA's ESMD a true purpose and destination once more.

Robotic precursor missions to asteroids and other destinations can certainly do some great science along the way, but NASA needs to make sure that the budget for true scientific exploration, as done by the amazing spacecraft of SMD, remains insulated and protected from the almost boundless demands of human spaceflight. Humans have a place in space exploration, as ambassadors and proxies for the human race as a whole, but robotic missions will venture to the far reaches of our solar system to study environments too remote or dangerous for humans to visit any time soon. Fortunately, there's plenty of space for both!

About the Author:
2011-07-18-spaceexplorationbook.jpgDr. Cynthia B. Phillips is a planetary scientist at the SETI Institute and author of over a dozen books, including Space Exploration for Dummies. Dr. Phillips acknowledges helpful discussions with Dr. David Morrison for this article.


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Exploring the deep seas could give us a similar perspective on the planet.

Neil Crag, actually, in terms of solar radiation, once we get outside the earth's magnetic field, living in space may well be unsafe.

By Thomson Voucher Code (not verified) on 20 Jul 2011 #permalink

In the not-too-distant future, artificial intelligence will allow vacuum-tolerant robots to think as creatively as we humans do. At that point, Earth-born intelligence can be launched into the heavens for both scientific AND exploratory purposes. It may not be quite as satisfying as human exploration, but it will be immensely cheaper and safer... until it comes time for settlement! THEN we send out the intrepid people to live in robot-built, pre-constructed, settlements.

Poverty, Hunger, Disease and War. All could have been ameliorated by now with all the money that has been squandered on adventures by egomaniacal clowns.

Isn't the ultimate goal of space exploration the founding of new colonies on different worlds? We need to develop reliable spacecrafts capable of transporting humans for that. Transporting humans is far more difficult than the transportation of robotic spacecraft. (humans need air, food and water: robots don't). We need to develop this technology now, if we want to use is it in the future.

I don't know of anybody who argues that we should not be putting robots or remotely controlled vehicles into space. For long trips like Voyager or running an interstellar probe they are probably the only option at present.

However for any space settlement, almost by definition, it is not a settlement unless people settle and there will always be some unforeseen thing to fix.

Space development has to include people.

A lunar settlement with 90 robots, controlled by people on Earth and 10 mechanics etc on site would probably be far more . productive than one of 100 people because the automata can work almost all the time. But it would also be more productive than 100 robots and no people as soon as something break down.

To pretend that living in space would be unsafe is nonsense when compared with the sort of risks we run down here. If all mining and fishing were already banned there would be a case.

If Christopher Columbus had to rely on robots, due to risks far more severe than anything in space development, we would still be waiting. As with many such scare stories I think it is more a function of the anti-technology campaigners inventing scare stories than of a genuine concern. If I am wrong such campaigners would be able to show that they had equally opposed equal or far greater existing risks.

Good article. Also, yes, I can see that scientific discovery and exploration are two separate entities. Until we can first master, or at least mitigate, the totally unfriendly-and-dangerous-to-humans aspects of `space travel', let alone sustenance during same, best leave it to the machines to gather data - kind of a no-brainer...

Wouldn't funding research into driving down the cost of getting 10,000 kg+ payloads into low earth orbit be the best way to spend dollars right now? That could ultimately decrease costs for manned "because it's there" missions, science missions, and commercial missions as well.

Robots are the way to go for the foreseeable future. Beyond providing awe inspiring images, they provide a wealth of necessary data. They can do mapping, environmental analysis, identify risks and resources, deploy long term monitoring equipment and lay the necessary groundwork for an eventual human migration beyond earth. For that to happen though, we will need a space elevator or other breakthrough technology that can significantly reduce the huge costs of moving humans into space. A man on the moon gives the USA bragging rights but we haven't been able to build on that despite decades of advancements in technology. I would love to see a mission to Titan. Robots are ready. Human astronauts aren't anywhere close.

Lets assume for a second we could get human explorers to Mars, and return them to the moon. They would have to be encased in pressure suits, so it would not be at all like exploring the surface of the earth, vision would be the primary sense used. At this robots can take as good a picture as humans can see. The reaction time to a discovery could be larger if new instruments are needed, (assuming the humans brought them). Lets take an earth environment where humans have to be enclosed in protective devices to survive the deep sea. It seems that ROV's are taking over that environment from human containing vehicles. The question is should humanity go beyond earth or just send memorials out into space (big memory devices) for the other life forms to find?

Exploring the deep seas could give us a similar perspective on the planet.

Neil Crag, actually, in terms of solar radiation, once we get outside the earth's magnetic field, living in space may well be unsafe.

Here's the "deep time" case for human exploration and development:

An organism that lives in only one ecological niche is more vulnerable to extinction than an organism that has migrated to many ecological niches. This is true on a cosmic scale, as it is on a planetary scale.

Earth is one ecological niche in the bigger picture. Eventually something will destroy it or render it uninhabitable. A sufficiently large caldera explosion could set civilization back hundreds of years. A large object impact could spell the extinction of complex organisms including ourselves. Billions of years from now the Sun will likely expand into a red giant that incinerates the inner planets. If the Sun was to explode, the outer planets would be unleashed to drift in the cold darkness.

Mars is a niche waiting to be occupied, that will liberate Earth life and memes from events that could destroy civilization or wipe out life on Earth. Interstellar development leads to an effectively unlimited series of niches, and liberates Earth life and memes from the loss of our solar system. By these things I do *not* mean that all or even most humans would migrate in the event of a threat, but only that the species as a whole, and whatever other species plural it brought with it, would continue elsewhere in the event that any one planet or star system was lost.

In order to do "Mars and the stars," we need an unbroken line of scientific and technical progress, we need adequate sources of stored energy and minerals, and we need economic surpluses on a national and planetary scale. The development of Mars to the point of planetary self-sufficiency and independence from Earth will likely require centuries of concerted effort. An interstellar colonization effort will likely require at minimum a multi-millennial journey for a colony ship that is effectively a self-sufficient civilization traveling at a respectable single-digit percentage of light speed.

The path to these goals will necessarily require patience and persistence through a series of small steps over a period of time longer than any that humans have considered in their plans during the entire history of civilization.

Mars is almost certainly feasible today, plus a few technical solutions such as how to land a large heavy object there (this is a serious sticking point according to people familiar with the issues). For the cost of the Iraq war we could have had our Mars program and sent a live mission there and back by now.

The key question for our space efforts today is, how do they fit into that long-term trajectory?

The only decision we do not have the right to make, morally, is the decision to turn our backs on the whole thing and thereby condemn our distant descendants to Darwinian failure on the cosmic scale.

Longterm human survival does require getting humans off the planetary surface.

But it doesn't actually require getting humans very far. A colony on Mars, or even the Moon, is not required.

All that is needed is earth orbit.

A series of self-sustaining colonies in earth orbit, whether constructed from materials boosted from earth's surface or obtained elsewhere in space, is that would be required. (They would have to be capable of complete self-sustaining independence, of course, and the more of them there are, the better)

That would be enough for all threats up to the Sun moving off the main sequence. And for this, self-sustaining orbital colonies capable of self-directed mobility (ie stick an engine on the thing so it can break orbit and move elsewhere if needed in an emergency), even if very slow, would be enough.

Finally, self-sustaining, self-directed mobile, and self-replicating (ie, the colony can move to a resource source, park there, construct a new colony structure, move a portion of its excess population into the new colony, and then part ways) would probably enough to colonize the galaxy.

There would, in fact, be no actual need for any human being to step foot on any world other than earth (except for voluntary exploratory and/or recreational reasons).


The problem with your version is that gravity is still the best way to get an atmosphere to stick around over the course of deep time.

A colony ship designed for interstellar travel might have to sustain an atmosphere for a few thousand years between its point of origin and its destination: but that's an eye-blink compared to the lifespan of a planet.

The path to these goals will necessarily require patience and persistence through a series of small steps over a period of time longer than any that humans have considered in their plans during the entire history of civilization.

This is the first time I have visited,this is a world-class write-up which I think should be read by every citizen of the world. I am happy that at least somebody gave this subject an attention.

Poverty, Hunger, Disease and War. All could have been ameliorated by now with all the money that has been squandered on adventures by egomaniacal clowns.
The only possible reason anyone might have to explore beyond the moon is to set up a place to escape to when the nest becomes so fouled and everyone is mulcted beyond their capacity to forgive.
Strutting little idiots.
The surest sign of intelligence in this galaxy is the fact that no on has seen fit to visit us and publicly proclaim their presence.

By James Bain (not verified) on 30 Jul 2011 #permalink

A big project and swallow a stunning budget. This course is expected to get results commensurate with such a large expenditure.

I enjoy that this is the 'headline' at Scienceblogs. Please keep up the incredibly excellent work.

By Douglas Watts (not verified) on 01 Aug 2011 #permalink