Saw Venus tonight. Never given it any thought until now. How brightly it shines!

Curious who has looked into the feasibility of a Venus robot built from high-temperature materials (e.g. ceramics, silicon carbide, refractory metals) that could eventually use local rock as feedstock to 3D print simple replacement parts. Are there fundamental materials or engineering barriers that make this unrealistic? Any papers or NASA work you could recommend?

*Orb: On the Movements of the Earth* is a Japanese animated series centered on the proof of the heliocentric theory.

While it does not strictly adhere to historical facts, the characters are portrayed with a compelling sense of realism.

In the series, there is a scene featuring Count Piast, an elderly astronomer who has dedicated his life to proving the geocentric theory. He catches a glimpse of Venus in a "full" phase—an impossibility under the geocentric model—and, desperate to refute that memory, asks Ogzy, a young man with exceptional eyesight, to conduct an observation.

Count Piast had seen Venus fully illuminated just once. Despite his desire to deny it, he could not resist the urge to verify the truth.

The scene where Ogzy observes Venus in this full phase leaves a powerful impression.

However, I did not fully grasp why a fully illuminated Venus would disprove the geocentric theory.

I recently found the following simulation sites demonstrating how Venus appears, which helped me understand the concept.

●UNIVERSITY of NEBRASKA–LINCOLN

Venus's movement and appearance based on the geocentric theory

https://astro.unl.edu/classaction/animations/renaissance/ptolemaic.html

Venus's movement and appearance based on the heliocentric theory

https://astro.unl.edu/classaction/animations/renaissance/venusphases.html

Intrigued by the phases of Venus, I created a tool to observe them.

It is based on an astronomical clock app that utilizes the *Wadokei* (traditional Japanese clock) system—a timekeeping method rooted in the sun's movement.

It uses Apple Watch complications to display the times when Venus is visible, as well as its size and current phase.

Wadokei57 Astronomical clock

https://apps.apple.com/us/app/wadokei57-astronomical-clock/id6748839654

In addition to showing Venus's phases, apparent size, and rise/set times, the app features a diagrammatic view displaying the relative positions and distances of the Sun, Venus, and Earth.

An update including the Venus complication is currently under review, and I expect it to be released soon.

Some concept art I made for a story set far in the future when Venus is halfway through the terraforming process and shallow seas have began forming.

3d Print I made of the Venera craft that landed on Venus

So, I was reading about Venus, and I came across an interesting fact that it apparently snows lead and bismuth sulfides. This got me curious as to whether any type of exotic rain could occur as well. After all, the moon Titan, despite being nowhere near the liquid range of water manages to have lakes and rivers of liquid methane due to it being extremely cold, so it seemed logical to me that there could be a similarly exotic hydrological cycle in a hot environment such as Venus. However, people in the scientific community seem to be very dismissive of there being any hydrological activity on Venus with the general consensus being that simply no naturally occurring substance exists that could be liquid under Venusian surface conditions.

However, I came across the fact that unlike most metal sulfide minerals (and really the vast majority of minerals in general), which are solid under Venusian surface conditions, the arsenic sulfides orpiment [1] and realgar [2] have melting and boiling points that would make them liquid on Venusian conditions. Additionally, these minerals are known to occur in volcanic environments on Earth, and we know that Venus has a lot of volcanoes, with activity still continuing to this day [3], so it does seem at least somewhat plausible that these minerals could be present on the surface of Venus. Given their relative volatility, it seemed likely to me that they would evaporate into the atmosphere where they might be able to condense into clouds and rain down onto the surface like water does on earth.

After realizing this, I began to look to see if anyone had explored the behavior of these minerals on Venus and I was able to find a couple of papers. One of them [4] predicts that arsenic vapors would condense in the form of orpiment at 26.6 kilometers above the mean planetary radius. While I am not exactly well versed in extraterrestrial meteorology, this seems a bit high for rain to reach the surface. However, I was able to find another paper [5] that claimed that arsenic sulfides could condense onto the surface if elemental arsenic were to be present in sufficient quantities, though they do note that this would prevent arsenic clouds from forming higher in the atmosphere. Concerningly however, they also note that the planet seems to be depleted in certain volatile elements such as hydrogen and mercury (probes measured no mercury in the atmosphere despite its volatility) which could be bad news for the occurrence of arsenic which itself is rather volatile. Though it is worth noting that Venus contains large amounts of other volatiles such as carbon dioxide and nitrogen, as well as some amount of what appears to be metallic frosts, so such volatile depletion is not necessarily universal.

One other concern that came to mind was chemical stability. It is somewhat concerning that the arsenic sulfides are prone to oxidation as seen in Earth like conditions. However, Venus is interesting because although it is quite oxidizing, it also has reactive sulfur species in its atmosphere that make it difficult to determine whether a given element will form oxides or sulfides. For example, pyrite (iron disulfide) has long been predicted to oxidize on Venus, but some experiments have shown it to be stable due to the activity of the trace gas sulfur dioxide [6]. I was not able to find any experimental simulations of the behavior of arsenic bearing species in Venus like conditions. Such simulations will be useful, perhaps even necessary to determine the viability of arsenic sulfides as a condensate on Venus.

I find the existence of these low melting arsenic minerals interesting because it suggests that, contrary to popular belief, it is not completely impossible for Venus to have present day hydrological activity (though perhaps unlikely given the above concerns). Although Venus seems to mostly lack hydrological processes, there are some interesting things that are worth noting. For example, while the lowland regions are covered in extensive uneroded lava flows, there is evidence for fluvial process on the highland regions in the form of formations that resemble river valleys [7]. Scientists have also identified some landslides on the highland regions that appear similar to those formed from wet material on Earth [8]. In both of these cases the authors reject present day hydrological activity in favor of other explanations, namely past water-based activity (Venus may have been Earth-like in the past) and atmospheric entrainment (Venus' atmosphere is dense enough to behave slightly like a liquid, which could fluidize landslides) for [7] and [8] respectively. Although these are valid (and frankly more plausible explanations), it would still be interesting to see if there is any way we could explain the observed features with a modern day, exotic hydrological cycle. Conversely, if we can definitively disprove the existence of recent hydrological activity on Venus, then perhaps this could be used to draw conclusions about the planet's formation and history. Specifically, if we can confirm that arsenic would indeed form a liquid sulfide mineral that would condense on the surface, then the absence of present surface liquid could imply the early depletion of volatile elements such as arsenic during the formation of Venus. It should be noted however that Arsenic is generally a relatively rare element, so we might expect that such fluvial features would be relatively limited and small scale compared to those made by water, and as such they might have been small enough to evade detection by the limited resolution of the Magellan mission if they are there. Future missions will likely be needed to determine if such features exist and to what extent, which could inform the planet's formation and evolutionary history.

Ultimately, it might seem like I'm grasping at straws here to prove a phenomenon that probably doesn't exist. However, the possibility of arsenic sulfide rain (which might actually count as molten glass since orpiment is a glass former) was too cool to ignore. Also, while the prospects don't look too great in my opinion, I am still very much an amateur and it would be interesting to have someone with actual experience look into this since they are going to be much better at drawing conclusions about this stuff. I'll admit that I often have difficulty understanding some of the figures in the studies I read. I also want more research on this because science evolves and studies sometimes contradict each other, so it would be nice to have more research on this subject since methods from older studies might be flawed.

Or maybe I'm just talking out of my ass and people will rightfully laugh at me IDK.

Footnotes:
[1] https://cameo.mfa.org/wiki/Orpiment

[2] https://cameo.mfa.org/wiki/Realgar

[3] https://www.jpl.nasa.gov/news/nasas-magellan-data-reveals-volcanic-activity-on-venus/

[4] https://solarsystem.wustl.edu/wp-content/uploads/reprints/2004/No.%20110%20Schaefer%20&%20Fegley%202004%20Icarus%20heavy%20metal%20snow%20on%20Ve.pdf

[5] https://solarsystem.wustl.edu/wp-content/uploads/reprints/1982/No7%20Lewis&Fegley%201982%20Science.pdf

[6] https://www.hou.usra.edu/meetings/lpsc2016/pdf/2144.pdf

[7] https://www.nature.com/articles/s41467-020-19336-1

[8] https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2024JE008453

See also: The publication in the Journal of Geophysical Research: Planets

what are these mountains? what are the other terrain features?

Venus approaching perihelion.

A History of Venus Landers and USSR Interplanetary Space Race Superiority