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Space Exploration

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    $\begingroup$ "Thus a distinction must be made between hardness of a Venusian mineral on Venus versus hardness under Earth-ambient conditions." - This can be resolved by stipulating STP/NTP when performing hardness tests. Wonder if a concept of "standard gravity" would also be needed...does gravity affect hardness? $\endgroup$ Commented Oct 12, 2020 at 0:49
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    $\begingroup$ "Does gravity affect hardness?" How much? Stress from gravitational forces would be very small compared with the stress scale factors (e.g. tensile strength) of a typical mineral, but deep inside the planet it could get big. Compressed material deep inside could well be harder than what we find on a planetary surface. Mineral hardness at STP/NTP is not possible with a material like nitrogen and yet their hardness and strength are important for building geological features on outer solar system bodies. $\endgroup$ Commented Oct 12, 2020 at 1:06
  • $\begingroup$ I've just asked How hard is the hardest ice in the solar system? $\endgroup$ Commented Oct 12, 2020 at 3:19
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    $\begingroup$ It is written here that: "certain types of rock is harder on the surface of the Moon or Mars than it is on Earth, whether it's because the minerals and pressure/temperature ranges are not found or because there are fewer mechanisms allowing deeper rock to rise to the surface". $\endgroup$ Commented Oct 12, 2020 at 4:38
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    $\begingroup$ Did I not distinguish between interiors and surfaces of planets in the.comment? $\endgroup$ Commented Oct 12, 2020 at 9:31