As far as I know, it isn't ethical to contaminate outer space with life from Earth, because then we will never be sure if life can actually grow there. However, I just read reports that the latest Chang'e-4 brings an entire ecosystem to the far side of the moon, with Arabidopsis plant seeds and even silkworms.

Is this okay? Even if it is contained within the machine and not spewed out? What danger is there of the plant material coming out of the machine and contaminating the moon?

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    $\begingroup$ What system of ethics? $\endgroup$ Jan 11, 2019 at 16:27
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    $\begingroup$ It's effectively impossible to prove a negative; we will never be able to claim with 100% certainty that any celestial body is completely devoid of life. Does that make the prospect of stellar colonization an unethical venture from the get-go? $\endgroup$ Jan 11, 2019 at 19:29
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    $\begingroup$ Space has dropped plenty of material on Earth; it's time we returned the favor. $\endgroup$ Jan 11, 2019 at 22:02
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    $\begingroup$ "...because then we will never be sure if life can actually grow there." ... The moon, lacking atmosphere, shielding from cosmic radiation, and a number of other important factors for life, is almost certainly never going to be able to support it. If by some freak accident that changes, it almost certainly won't be for millions or billions of years. Why is disrupting a hypothetical future that probably won't happen and that we have very little chance of realistically disrupting an ethical concern? I can only respond to this with "wat." $\endgroup$
    – jpmc26
    Jan 11, 2019 at 23:23

3 Answers 3


tl;dr: There are "96 bags of poop, pee, and puke" on the Moon already!

The bags of waste are ecosystems for sure, but like the ones you mentioned, they are not going to remain alive for very long

edit: ...or even potentially viable if brought in from the cold and incubated. Huge monthly thermal swings between say roughly +120°C and -120°C (see here and here for example) will render all except the heartiest extremophile spores nonviable. (see answers here and here)

For those extreme spores that somehow snuck aboard Chang-e 4 or the Apollo astronauts' digestive track, the lack of a lunar atmosphere will expose their DNA to cosmic radiation, and while the UV may be absorbed protons and to some extent neutrons and gamma rays from the surface will hopefully slow-roast their DNA to non-viability in short order.

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From Gizmodo's There's Poop on the Moon:

There is, however, scientific value to the things left behind. Astrobiologists, for instance, hope to one day inspect that half-century-old feces to see if the crap has undergone any genetic mutations while in space. Even more mundane gear on the moon's surface offer a unique perspective on how different materials hold up in extreme environments like the moon, where temperatures oscillate between minus 370-degrees to 250-degrees Fahrenheit.

What kinds of mundane gear, you wonder? Well, there's actually an entire website devoted to trash on the moon. However, here's a list of the more interesting and unusual items—aside from the 96 bags of poop, pee, and puke:

  • More than 70 spacecraft
  • 5 American flags, all of which are now white
  • 12 pairs of boots
  • An olive branch sculpture made of gold:
  • "Several improvised javelins"
  • Used wet wipes
  • Space food wrappers
  • 2 golf balls
  • This gold-plated telescope that was the first tool used to make astronomical observations from the surface of another planetary body:
  • A feather from Baggin, the official mascot of Air Force Academy
  • A patch from the doomed Apollo 1 mission that never launched
  • This silicon disc with goodwill messages from 73 world leaders:
  • 12 Hasselbad cameras
  • This photograph of Astronaut Charlie Duke's family from Apollo 16:
  • Not to be repetitive or anything: 96 bags of poop, pee, and puke


According to Jainism and some forms of Buddhism, the concept of Ahisma tell us that it not ethical to bring an ecosystem of living creatures to an environment that will almost assuredly kill them as a result of you bringing them there.

Ahinsā (Ahinsā) in Jainism is a fundamental principle forming the cornerstone of its ethics and doctrine. The term ahinsa means nonviolence, non-injury and absence of desire to harm any life forms.... Furthermore, the Jains extend the concept of ahinsa not only to humans but to all animals, plants, micro-organisms and all beings having life or life potential. All life is sacred and everything has a right to live fearlessly to its maximum potential. Living beings need not fear those who have taken the vow of ahinsa.

Emphasis mine. Whoever decided to put those organisms on the vessel did so either knowing it would harm them, or if not, at least were not able to be sure that it wouldn't hamper the creatures' maximum potential.

From the article linked:

so it’s unclear whether plants and worms will grow normally with the moon’s meager 17 percent gravity.

To the Jainist belief system, that was an unethical action.

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    $\begingroup$ +1 for looking at the question in exactly the opposite direction to everyone else! $\endgroup$ Jan 11, 2019 at 23:37
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    $\begingroup$ So what? There are thousands of gods and religions on earth. Whatever you do is going to be considered unethical by at least one religion. $\endgroup$ Jan 12, 2019 at 0:50
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    $\begingroup$ Eric, the only difference between Jainism and the western Hippocratic oath is that it extends to all forms of life. This is hardly a stretch and I think it is remiss to dismiss it outright simply because the ethical framework has religious roots. $\endgroup$
    – Caleb Jay
    Jan 12, 2019 at 20:27
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    $\begingroup$ @CalebJay I like this answer for the lateral thinking but just be clear religion is not necessary to build a ethical framework (this path is dangerous because on this way one can falsely claim atheist are amoral and the "wrong religion" is immoral) $\endgroup$
    – jean
    Jan 14, 2019 at 10:18
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    $\begingroup$ A similar document could perhaps be a person's manifesto. I would argue that the Jewish "thou shalt not kill" would also indicate the action was immoral based on that religion's grounds. Basically, I don't think me posting "Killing creatures is bad, and therefore this was immoral" would be enough of an answer. $\endgroup$
    – Caleb Jay
    Jan 14, 2019 at 20:03

Humans have already been to the Moon, and pretty much verified it is completely sterile. It isn't really an issue bringing plants to the Moon, it couldn't contaminate anything, as there is nothing there it could really affect. Besides, anything complex couldn't survive in a vacuum, and there's been plenty of bacteria that have been on the Moon from the Apollo missions to previous landers.

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    $\begingroup$ I am not sure "pretty much verified it is completely sterile" is an accurate statement. Related Can the vacuum of space be used to sterilize equipment?. I believe there is also a post about how much moon dirt you need to to protect from radiation but not finding it. Realistically there could be an entire ecosystem thriving under the surface of the moon. Maybe not a high potential, but it can't be ruled out. $\endgroup$ Jan 11, 2019 at 18:00
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    $\begingroup$ @JamesJenkins according to this about half a meter of regolith is required. That aside, we’ve found precious little to indicate any possibility of life on the Moon. I suspect Titan would be a better candidate for extraterrestrial life. $\endgroup$
    – Snoopy
    Jan 11, 2019 at 21:34
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    $\begingroup$ With 9 sample return missions, if there is life on the Moon, it is hiding really well. $\endgroup$
    – PearsonArtPhoto
    Jan 11, 2019 at 21:35
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    $\begingroup$ Even the toughest Earth-derived bacteria can't do more than just sit there hoping that some water will eventually show up. The Moon is an incredibly hostile environment. $\endgroup$
    – Mark
    Jan 11, 2019 at 22:07

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