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1

Altho I'm a Mars Dust Devil researcher, my work is mostly conducted on terrestrial desert analogs (so I'd want to check my details if this were crucial... ). My understanding is that 1) the dust is re-cycled so much it's now very fine clay (2-4um), dry and often recently draped over surface roughness elements. Meanwhile, 2) weathered quartz leads to fine ...


3

As a Mars dust devil guy, I can say that the ubiquitous dust is NOT generally considered sharp-edged. Almost all of it is one of several clay minerals. Due to the absence of open water and given that the dust has been recycled continuously over many millennia (eroded, transported, deposited, re-eroded, etc), that dust is uniformly fine (2-4$\mu$m), "soft" (= ...


2

Not yet, but Mars 2020 will. Scott Manley did a video on the subject, starting somewhere around here. Basically Mars 2020 will fire lasers at something, listening to the sounds it makes and that can tell it something about the composition of the surface. You can read more about that on NASA's website.


7

Update 2 The taper ratio formula seems to be correct. The crosscheck stress calculation error mentioned in the Update 1 below is found to be due to: a) incorrectly calculated tether volume (and therefore mass). I assumed a linear change of cross section area across the tether length. In fact, to achieve the uniform strength, a logarithmic increase in erea ...


2

The solar tide is slowing the rotation of Venus down. A general rule of tidal effects on rotation goes like this: tidal forces will cause the angular momentum vector from rotation to match the vector from orbital motion. For example, consider the Earth and its Moon. Earth's rotational vector is pointed north with a magnitude of $2\pi$ radians per day. ...


1

Beyond the Roche limit orbiting material coalesces forming an object (a planet or moon, depending on whether said material is orbiting a star or a planet, respectively), within the Roche limit orbiting material disperses and forms rings. Much as objects have a Schwarzschild radius which traps light (the escape velocity is equal to the speed of light) they ...


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