How would you justify hidden aliens on Mars, which no one on Earth has discovered yet?

I was thinking over it, and having them be primitive or highly advanced seems a necessity. The latter gives access to unknown stealth tech and advanced concealment methods, the former means we can't pick up their radiowaves as there are none.

Secondly, it would seem they'd have to not do much on the surface. Maybe the rocks we keep mistaking for faces would be their monuments. Most of their time would be spent underground, and some kind of underground ecosystem may be necessary for Mars?

The aliens in their culture should probably be aware of Earthlings, and not like the Earthlings watching them, and so avoid being seen. Using telescopes beyond their technological expectations. If they watch Earth closely, and pay attention to incoming satellites, they might be able to have a culture focused on avoiding being seen by such. Assuming the humans would kill them all, if they were found out.

Note that I'm not concerned about the aliens evolving on Mars. Just that they can live there and hide.

  • $\begingroup$ They'e highly technical visitors, and they can control the data our probes send back would be the easiest way. Extrapolate to controlling data Earthside and they can do it in plain sight if we could see them. $\endgroup$
    – Kilisi
    Nov 16, 2016 at 12:19

4 Answers 4


We have high resolution images of the entire surface, with a pixel resolution of 1 foot (that’s higher than what you get on Google Earth, for comparison).

So they can’t leave anything laying around, and can’t interact with the surface or outside resources in any large scale or we’d see something happening even if camouflaged. Even if dug in and using internal power, if there was substantial activity it would show up as a heat signature.

So, they would have to be a very small presence. A single base, for example, could take care to camouflage and disguise itself, especially if they know the particulars of our instruments.

There are phenomena that we have seen that are not fully explained, or are presumed to be some geologic process. You might find something interesting there to explain in your story as actually being artificial.

  • $\begingroup$ Yeah, it is a difficult problem. I figure having the aliens live underground and avoid the satellites skillfully is the way to go. All their civilization is under enough ground that IR won't pick it up. Possessions and the like are probably valuable enough they won't leave anything special out in the field. Especially since they're scared to death of the watchers. $\endgroup$
    – J. Doe
    Nov 15, 2016 at 23:22

What We Know

Right off the bat, it's necessary to list everything we know so far. This will help us decide what aliens need to do to hide.

  • True color pictures of the surface
  • Atmospheric composition data (we'd know if they were breathing, etc)
  • Ground / soil composition data (mostly iron oxide and igneous rock)
  • Data on underground structures up to 1 kilometer deep
  • Lack of abundant radio waves, etc (communications)

More importantly, we don't have information on

  • Underground structures deeper than 1 kilometer
  • Surface microbiology (we haven't looked for bacteria)

Therefore, life on Mars, unless it burrows in tunnels that look like lava tubes, probably fits in your categories of "primitive" (surface microorganisms) or "advanced" (living deeper than 1 km).

Analyzing the Question

  • Unquoted parts of the question are things that I agree with 100%

The latter gives access to unknown stealth tech and advanced concealment methods

Technically yes that is possible, but necessary? Not necessarily. If we only see up to 1 km below the Martian surface, but humans can bore holes 12 km deep, your aliens may be at the same place as we are technologically - just not spacefaring, because we'd probably know about that.

Maybe the rocks we keep mistaking for faces would be their monuments.

Scientists have repeatedly disproved these "faces", and we can see the entire surface, so if there are any monuments, they're buried deep under some iron oxide. * Deeper than 1 km, because we would detect them if they were close to the surface.

The aliens in their culture should probably be aware of Earthlings,

Debatable. If these aliens buried themselves when they knew Mars was losing its atmosphere (assuming they evolved there) and we don't see any Martian satellites, chances are they aren't aware of us. Unless they hid their satellites in asteroids, etc.

not like the Earthlings watching them, and so avoid being seen.

This is actually spot on! A barren planet on which the only culture lives underground may not be equipped to handle invasion or threats. Therefore, being seen is incredibly dangerous.

If they watch Earth closely, and pay attention to incoming satellites, they might be able to have a culture focused on avoiding being seen by such.

If we can see isolated asteroids and small objects in space, we can probably see whatever these creatures watch with; it's not very easy to hide in space. Still, avoiding being seen is accurate - it just might involve staying underground instead of active avoidance.

Note that I'm not concerned about the aliens evolving on Mars. Just that they can live there and hide.

Hiding is reasonable, but so too is evolving.

  • $\begingroup$ Good response, thanks! What I meant with the telescopes, is imagine a more or less modern level of understanding of telescopes, binoculars, and other long-distance viewing apparatus. Despite the fact they're going around with spears and swords still. With watching Earth, I figured they'd study it much the way ancient people studied Mars, watching it with large telescopes. Eventually, by luck or by some other encounter with aliens, they'd figure out there were people on Earth before Earth figured out there are people on Mars. They'd then go to great lengths to hide their presence. $\endgroup$
    – J. Doe
    Nov 16, 2016 at 1:31
  • $\begingroup$ @J.Doe Sounds mostly reasonable, although it may take more than spear and sword technology to build an ecosystem so far underground. Consider an alternative: they are at current human technology and "discover aliens on Earth"; that would allow them to migrate underground realistically while also using telescopes to observe. $\endgroup$
    – Zxyrra
    Nov 16, 2016 at 3:28
  • $\begingroup$ I think some sort of natural underground ecosystem will be necessary for these Martians. Ones based off radiation are the most common scifi. $\endgroup$
    – J. Doe
    Nov 17, 2016 at 5:32
  • $\begingroup$ @J.Doe Natural ecosystems below 1 km in depth are unlikely to evolve; generally they would be within 1 km of the surface, but scans with the MRO show no signs of these. Maybe an artificially introduced ecosystem would work deeper. $\endgroup$
    – Zxyrra
    Nov 17, 2016 at 5:42

For the reasons mentioned by the other posters, we would have detected a surface settlement and we would probably have detected a solitary lander. (If it was covered by dust, there is the possiblity that we haven't examined out pics closely enough to notice.) So it must be a deliberate effort to avoid detection.

So why are the aliens hiding?

Take all the reasons why they might hide on Earth. A Prime Directive. Or more sinister purposes.

Depends on how silly you want to get -- there is nothing on Earth that would pay the transport costs in a setting, with the possible exception of information (arts, genetic data, and so on). So assume that there is FTL, and that they can get something from Earth. Getting it is easier if mankind doesn't know they are here.

Why go to Mars instead of Earth?

Perhaps the aliens were involved in that little incident in Roswell. Afterwards they decided that Utopia Planitia is a better basecamp than New Mexico. Mars offers many advantages:

  • Not many random visitors. If a probe lands too close, zap it.
  • More friendly than Venus or Mercury, higher gravity than Luna.
  • $\begingroup$ "nothing on Earth that would pay the transport costs" is cause for disagreement - loads of information, a planet that's mostly stable and won't expire for some time, diverse natural resources, food if they can ingest it, abundant metals to build more ships, potential workers, etc $\endgroup$
    – Zxyrra
    Nov 17, 2016 at 5:45

The most probable scenario for hidden alien life on the planet Mars is submartian colonies of microbiota. These organisms may be similar to the deep subterranean micro-organisms discovered in mines on Earth. Since they live out of sight and have so far been not detected by Mars missions to date. The presence of methane is a possible signature for biological activity. Where "possible' means that non-biological sources of methane cannot be ruled out.

Now considering the possibility of technologically advanced hidden aliens on planet Mars, there are two possible scenarios.

Firstly, a native Martian technological civilization. This may be the least likely scenario. However, it would have to have the following characteristics. If the Martians lived on the surface of their planet they must have done so in the ancient past. No longer able to survive on the surface of Mars they have constructed deep submartian habitats and live down below. Interestingly the interior volume of a planet is extremely large. if any technological civilization could develop the machinery to excavate habitats underground. create life support, and food production facilities they would have access to a volume of living space comparable to a small dyson sphere. If our hypothetical hidden Martians had pursued this developmental path, they would have remarkably little interest in what goes on outside the surface of their planet.

Secondly, the hidden aliens on Mars aren't native lifeforms. They didn't evolve in our solar system, and have come from elsewhere in the galaxy. Considering it is highly probable that sapient life is rare in the cosmos, any spacefaring species that discovered another sapient species would want to keep it under observation.

Not just because it would be interesting to observe a sapient species, but it is very probable that sapient species will spend a long time before they develop a technological civilization. It took our species of the order of a million years to go from having evolved to sending probes into space. It can be expected there will be a long technological plateau once our science and engineering have attained maturity. Bigger, better, faster, more and more of it, like, well, Moore's Law, isn't necessarily justified. Sooner or later we will hit a limit to what we can understand or manipulate in the physical world, this technological plateau could last for many megayears.

This suggests finding a sapient species on the cusp of transitioning from the long paleaolithic plateau to a possibly even longer astrotechnical plateau will be exceptionally rare. Galactic scientists would want to observe such a civilization in its transition phase.

For this reason, they could establish a concealed base on Mars as their main base of operations. Surveillance craft could dispatched on a regular basis to observe and record developments on Earth.

Why Mars and not the Moon? Well, galactic observers have probably used the Moon, but they will have disassembled any lunar outposts, knowing humans are going to explore our satellite at some time in the near future. Not disturbing our development will be an imperative of their observation and research program. If humans discovered the presence of aliens this would send our developmental path down some unexpected trajectory. However, Mars has better gravity for sapient organisms than the Moon. In fact, the aliens may have come from a planet with gravity closer to that of Mars than the Moon's.

If their base is concealed deep underground the aliens could have factories and food production facilities. There they can build everything they need for their research. On Earth 3D printing is a new technology, but for an ancient spacefaring species 3D fabrication will be advanced to the nth degree.

This model of alien living and hiding on Mars fulfills the requirement that they just live there and conceal themselves. They're not Martians coming from elsewhere and are there to conduct high-level xenological research into the civilizational development of the sapient species living on the third planet of our solar system. Also, they possess the technology to easily conceal themselves.


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