Nonterrestrial artifacts hard to pin down

November 7, 2011

( -- Two Pioneer probes left our solar system carrying plaques about humankind, and two Voyager probes will soon join them to gather information about places far out in our galaxy. We can and will send more autonomous probes into outer space, but why have we never found evidence of other civilizations doing the same? A pair of postdoctoral researchers at Penn State, approaching the problem mathematically, shows that we have not looked in enough places to ensure that no extraterrestrial artifacts exist in our solar system.

"The vastness of space, combined with our limited searches to date, implies that any remote unpiloted exploratory probes of would likely remain unnoticed," report Jacob Haqq-Misra, Rock Ethics Institute, and Ravi Kumar Kopparapu, Earth and Environmental Systems Institute, in a paper accepted by Acta Astronautica and posted online on ArXiv.

So far, we have not found any nonterrestrial artifacts in our solar system. The , originally formulated by , asks, if is common, why have no technological civilizations been observed. Answers to this question could include life is rare, intelligent cultures inevitably destroy themselves, intelligent beings have not gotten here yet or they are here but not revealing themselves. Even without actual contact, like us, other civilizations could be sending unpiloted probes to quietly peek at our civilization.

These probes, like ours, would be small and might be hidden in a variety of places. In the they would probably go unnoticed, especially if these nonterrestrial objects are only 3 to 33 feet in size, weighing little more than a ton.

"Extraterrestrial artifacts may exist in the solar system without our knowledge simply because we have not yet searched sufficiently," said Haqq-Misra and Kopparapu. "Few if any of the attempts would be capable of detecting a 1 to 10 meter (3 to 33 foot) probe."

Haqq-Misra and Kopparapu use a probabilistic method to determine if we have looked closely enough anywhere in the solar system to definitively say there are no nonterrestrial objects here. The analysis is based on answering the question, how sure can we be that we should have already found any nonterrestrial objects lurking in the solar system.

They view the solar system as a fixed volume and figure out the percentages of that volume that would need to be thoroughly searched using a discovery capability small enough to detect these probes, assuming that the probes are not consciously camouflaged. The researchers note that most searches to date have not been fine enough to locate such small probes or to totally rule out anywhere.

After taking into account a variety of potential biases, such as "the universe is teeming with life" or "life is rare," the team developed an equation that can be applied to a portion of the volume of the solar system and determine whether sufficient searching has been done to ensure that we can say there are no nonterrestrial objects within that volume.

The researchers found that it is, at this point, difficult to say that there are not nonterrestrial objects in our solar system.

"The surface of the Earth is one of the few places in the solar system that has been almost completely examined at a spatial resolution of less than 3 feet," said Haqq-Misra and Kopparapu.

But even as humans have spread across the solid surfaces of the Earth, there are still caves, jungles and deserts as well as the ocean floor and subsurface areas that have not been explored. Even with this, the Earth does have a high confidence that no nonterrestrial artifacts exist.

The moon and Mars have been searched to a small extent. An ongoing mapping project, the Lunar Reconnaissance Orbiter, is looking at the moon at a resolution of about 20 inches, so we may eventually be able to determine if there are no nonterrestrial objects on the moon. The researchers caution that surface maps may not be sufficient to distinguish between a space probe and a rock.

The surface of Mars is still mostly unsurveyed and the researchers' confidence in the probability of no nonterrestrial artifacts is low. Similarly, locations like the Earth-moon Lagrange points, the asteroid belt and the Kuiper belt might also shelter extra solar system probes, but the vast majority of the solar system's volume is uninvestigated.

"Searches to date of the are sufficiently incomplete that we cannot rule out the possibility that nonterrestrial artifacts are present and may even be observing us," said Haqq-Misra and Kopparapu. They add that "the completeness of our search for nonterrestrial objects will inevitably increase as we continue to explore the moon, Mars and other nearby regions of space."

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2.6 / 5 (7) Nov 07, 2011
"So far, we have not found any nonterrestrial artifacts in our solar system. The Fermi paradox, originally formulated by Enrico Fermi, asks, if intelligent life is..."

Fermi was a genius for his time, but the so-called Fermi paradox was shortsighted. It has been rebutted ad nauseum.

In essence, Fermi's assumptions were wrong. Of primary importance, the assumption that other cultures would be interested in being seen by us. This represents a not-uncommon ethno-centric (Terra-centric?) arrogance of classical thinking and should be disputed by progressive minds. The fact is, many reasons exist why we have not (at least not conclusively) observed and/or communicated with nonterrestrials. This does not in any way change the potential for or abundance of life throughout the universe.
5 / 5 (4) Nov 07, 2011
The Fermi paradox includes the idea that intelligent life will spread out by colonizing one solar system and then venture on to another. Only at the fringes of such colonization will evidence for them be hard to find. Any life colonizing our solar system will have left dramatic changes--mines at least on Mars and Earth to enable them to create spaceships to move on elsewhere. Only where intelligent life is first exploring will there be difficult to find evidence of their presence. Of course, they may have come and decided to be hidden to study us (the Zoo hypothesis). But that is not the argument of this paper.
1.7 / 5 (3) Nov 07, 2011

Your comments are inaccurate. Fermi himself postulated that if life were as abundant as others had claimed, then we should have seen some evidence. And yet, we do not.

Many others later connected themselves with Fermi's "paradox" and expanded upon the discussion. But Fermi's comments were simple and to the point.

This research directly addresses the shortcomings by attempting to show mathematically that Fermi -- like other of his contemporaries -- simply failed to see the proverbial forest for the trees.

In other words, over-optimistic estimates of both the probability of nonterrestrial life and our ability to "observe" it combined to give false importance to the paradox itself. Indeed, how many times will scientists let ego override factual evidence in the same way many in science would criticize, for example, a religionist for letting "faith" substitute for facts? Which is to say, Fermi's "paradox" was irrational to begin with, but his name alone carried weight.
4.2 / 5 (5) Nov 07, 2011
Maybe ETs know we are here and don't want to associate with the self-centered barbaric, savages of Earth.
5 / 5 (5) Nov 07, 2011
I think that there are a few important facts that make this issue essentially unresolvable for the current time.

First, we do not know how easy it is to travel far distances. Perhaps it is impractical or impossible to travel faster than the speed of light. Even if there is plenty of intelligent life, that doesn't mean that expansion is common.

Second, any object or probe would have had to arrive relatively recently (On geological time scales) to be recognizable. Even the stuff we left on the moon is being slowly degraded by UV, cosmic rays, micrometeorites...

Third...and by far most importantly...even if we can 'see' an extrasolar or extraterrestrial close would it have to be for us to recognize it as such?? I be that our capabilities to identify one of these objects would cover less than 1% of the solar system - and we've likely searched far less than that.

But yeah, I still think we should keep an eye out, just in case we get lucky.
3.4 / 5 (5) Nov 07, 2011
"even if we can 'see' an extrasolar or extraterrestrial close would it have to be for us to recognize it as such?? I be that our capabilities to identify one of these objects would cover less than 1% of the solar system - and we've likely searched far less than that" - that guy

This makes perfect sense. We tend to get a little excited about our own capabilities, but it's obvious every time we "discover" another rock close to or on an approach to Earth that we don't have even a small portion of local space mapped to any degree of accuracy.

When you take that out a couple more AUs, we are literally making new discoveries every day. With 2011 technology. Almost anything could have come here, parked in orbit tucked in close to or on a big rock, and we'd have no way of knowing if intelligent beings were in our "backyard" waving to us right now.
5 / 5 (3) Nov 07, 2011
I seriously doubt any civilization able to traverse space to get here would have even the slightest problem staying hidden indefinitely, most likely in plain sight~ the easiest way to fool humans.
not rated yet Nov 07, 2011
Given our own achievements in miniaturization, I'd suggest that getting 'here' at near the speed of light with a sophisticated 'something' that could examine an atmosphere, survey a planet and return home with a 'sample' will become increasingly easy and far less costly.
I realize that the "Space" industry is intent on using the US government to gain lots of income in the pursuit of getting 'man' into space, but acquiring the information that a manned exploration could would be much much less expensive using robot vehicles.
5 / 5 (1) Nov 08, 2011
if intelligent life is common, why have no technological civilizations been observed. Answers to this question could include life is rare, intelligent cultures inevitably destroy themselves, intelligent beings have not gotten here yet or they are here but not revealing themselves.

I could think of a number of other reasons:

a) Civilizations that depend on technology will become more efficient with time - which means that more energy is being diverted to do what you want to do and less is diverted into losses that could be detected by others.

b) Civilizations that do not depend on technology will not be obvious as they are well adapted to their environment.

c) Civilizations where individuals have reached effective immortality will become risk averse and probably not live on planets anyhow - but move off into deep space.

d) There's absolutely no point for a superior civilization to contact an inferior one.

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