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The Chinese space craft that just landed on the moon had a tube with a biosphere in with flies and plants. What are they expecting to learn? Didn't we already experiment that on the ISS?

enter image description here

Source

Chinese scientists released this image of a cotton plant germinating in its tank on the moon aboard the Chang'e 4 lander. The photograph was taken Jan. 7, 2019. Credit: Chongqing University

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    $\begingroup$ Your title is unclear on which part you're asking about. Do you mean why did they send this stuff to specifically the far side of the moon, as distinct from some other part of the moon? Or why did they send this specific stuff, rather than something else? In either case, I suspect the answer is that they wanted a mission that included living things, they wanted a mission to the far side, and the living things don't care which side of the moon they're on so they may as well kill both birds with the same stone. $\endgroup$ – David Richerby Jan 17 at 11:49
  • $\begingroup$ Sorry to break it to you, but the cotton plants have died. $\endgroup$ – JPhi1618 Jan 17 at 16:19
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The capsule and its seeds are stored on the Chang'e 4 lander. It protects the biosphere from the positive +/-200C degree temperature swings. They are basically experimenting to see how life evolves and survives in near zero gravity. Unlike the ISS where they essentially tested the same concept just in Zero Gravity. Learning this will better prepare humanity for populating other planets as well as long space travel time.

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Some of the information contained in this post requires additional references. Please edit to add citations to reliable sources that support the assertions made here. Unsourced material may be disputed or deleted.

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    $\begingroup$ Do they have counter plans in case the plants get sick and so on? $\endgroup$ – Geordi La Forge Jan 15 at 18:11
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    $\begingroup$ The unprecedented plan to create life in outer space is the most intriguing part of China's lunar probe mission later this year, and could be a major boost for dreams that humans will one day live on the Moon. "Our experiment might help accumulate knowledge for building a lunar base and long-term residence on the Moon," Professor Liu - So yeah, I assume they do have contingency plans. $\endgroup$ – KingsInnerSoul Jan 15 at 18:12
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    $\begingroup$ @GeordiLaForge Counter plans like what? It's on the far side of the moon. If it dies, it dies. $\endgroup$ – Graham Jan 15 at 22:48
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    $\begingroup$ @Graham Doesn't preclude contingency plans, like designing the experiment with two redundant chambers, so that the opportunity for science isn't wasted. Like the backup spider they flew on the ISS. $\endgroup$ – user71659 Jan 16 at 0:17
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    $\begingroup$ "They are basically experimenting to see how life evolves" - I haven't seen any indication that multiple generations and evolution are part of their scientific plans for this mission. Any source for that? $\endgroup$ – Mołot Jan 16 at 19:10
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Right now, almost 100% of existing research on growth in gravity fields is basically at 0g (ISS/Mir/Skylab/whatever) or 1g.

There are a lot of questions of what happens at 1/6g or 2/3g? No good experiments to demonstrate.

Thus the Chinese lander is testing 1/6th g.

SpaceX is likely to brute force test 38% g when they get to Mars. It is entirely possible that mitigation techniques developed for 0g are not useful or needed or effective at 38% g.

The Space Studies Institute (Via Gary Hudson, of Rotary Rocket infamy (alas)) is pushing for something they call G-Lab, an orbital facility with a control facility, at 0g and then a centrifuge at some other value.

If you are interested in this topic, there is an excellent "The Space Show with David Livingston" episode where Gary Hudson discusses this issue. The Space Show does not allow transcripts so I cannot link to anything like that, you are left with only listening.

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    $\begingroup$ I suspect it would actually have been cheaper to build a dedicated ⅙g artificial-gravity mission in LEO for these experiments (basically need only tether the tubes to a counterweight and spin it up with a monopropellant thruster), than to add them to the moon mission with its much higher Δv demand. Just, “first plant in ⅙g” doesn't have quite the PR ring that “first plant on the moon” has. $\endgroup$ – leftaroundabout Jan 15 at 22:31
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    $\begingroup$ Putting a small spinning plant on the ISS seems a lot easier for low G experiments too, even just two hanging flowerpots on a string, or a centrifuge $\endgroup$ – Xen2050 Jan 16 at 4:18
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    $\begingroup$ @leftaroundabout: A low-g centrifuge in LEO would only test growing plants in a centrifuge in LEO. Growing them on the moon tests growing them in the actual lunar environment. Of course for a full test, they should have scooped up some lunar "soil" and tried growing plants in that. $\endgroup$ – jamesqf Jan 16 at 5:18
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    $\begingroup$ @jamesqf I highly doubt that plants would survive in lunar regolith, at least without a lot of pre-processing. Both on the moon and on Mars, the first plants will be grown hydroponically and more or less completely isolated from the environment, save for the gravity, and that again is pretty much perfectly emulated by a centrifuge. (You may object that a centrifuge also generates Coriolis force, but that's hardly relevant for a plant because nothing in it moves fast.) $\endgroup$ – leftaroundabout Jan 16 at 8:51
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    $\begingroup$ "at 0g (ISS/Mir/Skylab/whatever) or 1g.": you should specify where the 1g experiements are. (Kidding.) $\endgroup$ – msh210 Jan 16 at 10:38
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They did it for propaganda or pride mostly. What sprouted quickly died because it froze. They did not have a method to protect the biosphere from the temperature swings. This is what they expected and admit.

The Chang'e-4 probe entered a "sleep mode" on Sunday as the first lunar night after the probe's landing fell. The temperature could drop as low as about minus 170 degrees centigrade.

"Life in the canister would not survive the lunar night," [experiment designer Professor] Xie [Gengxin] said.

(Xinhua)

There was no intention of seeing how well plants grow to any level of maturity. All they did was prove a seed can sprout at 1/6g. If a seed can sprout at 1g or 0g, I think it is safe to assume it would sprout at 1/6g. They might have proved a seed can sprout outside the protection of Earths magnetosphere, but the moon is sometimes in the tail of our magnetosphere. I'm not sure if it was at this time. Testing if the cumulative radiation dose over such a short mission would damage a seed could have been tested on earth. There was no real scientific value in this experiment that was not also obtainable for less effort and cost. The logical conclusion is that it was done for human emotional reasons. I'm not knocking them for that, I think it's cool.

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    $\begingroup$ Seems like there's a contradiction here; another answer says they did have a way to protect from temperature swings. Can you add a reference for the lack of protection, especially if from official Chinese sources? $\endgroup$ – Nathan Tuggy Jan 17 at 3:25
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    $\begingroup$ Several articles have bits and pieces from Professor Xie Gengxin (head of "experiment"). If you search his name you can find many quotes. Here is an example: xinhuanet.com/english/2019-01/15/c_137745505.htm If you dig thru the articles found by searching him you will see some fancy wording about "special" aluminum alloy materials and such. Which is a dead tell for propaganda in China or North Korea. Unless they invented transparent aluminum, it's BS. Here is the kicker: "Life in the canister would not survive the lunar night," Xie said. Parse the words Would not vs Did not. $\endgroup$ – Diznaster Jan 18 at 4:31
  • $\begingroup$ Can you show an article where they explained their heating mechanisms and biosphere climate controls? $\endgroup$ – Diznaster Jan 18 at 4:32
  • $\begingroup$ "propaganda and pride mostly" and to provide the scientists and engineers involved some practical experience $\endgroup$ – noɥʇʎԀʎzɐɹƆ Jan 18 at 6:07
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    $\begingroup$ I believe @NathanTuggy's comment was not a challenge, Diznaster, but a suggestion as to how you could improve the quality of your answer. $\endgroup$ – JCRM Jan 18 at 10:57
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They ran a competition for an experiment to make use of spare capacity on the lander. This one was chosen, most likely for it's potential to cultivate interest in the mission.

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