EDIT: I eventually managed to find the absorption spectra of SO2 online - it absorbs in the ultraviolet range only, not in the visible light range, so the only factor affecting light transmitting through the atmosphere will be the level of sulfur vapor humidity. Sections of the question have been struck out or added (in bold) to reflect this.
Question: I'm having trouble (after lots of googling and reading) finding information on the physical properties that the atmosphere and oceans would have - specifically, the penetration of light and transmittance of sound through the atmosphere and seas.
The only relevant information I found was from Freitas' famed Xenology book, which said of atmospheric sulfur vapor "At 1 atm pressure, blue light is cut to below human eye visibility in less than half a meter, and the red is gone in fifty meters. So if the partial pressures of [sulfur vapor] exceed perhaps 0.001-0.01 atm, no light of any color will be able to reach the surface of the planet from the outside"
I couldn't find anything for
sulfur dioxide in the air (see edit at top) or liquid sulfur.
My specific questions are:
What will the lighting conditions be like?
- What would the effect of sulfur vapor humidity in the air be on visibility? Specifically, what partial pressure of vapour seems reasonable? (I can approximate from the quote above from Freitas)
How far will light penetrate through the sea?
How much light will reach the surface? What wavelengths will penetrate the atmosphere? (presumably only the yellow color of the liquid sulfur's own color would penetrate through the sea itself for any appreciable distance)
How far and how well will sound travel through the sea?
How effective would detection of electric fields be in a sulfur sea? (E.g. for prey detection, as in sharks)
I don't need super accurate answers; ballpark figures in terms of comparisons to earth atmosphere and oceans would be fine - e.g. that light penetration at 1 meter depth in the sulfur sea would be equivalent to 1km in the earth's oceans.
The species of focus (which I expect I will have other questions about later) lives around the ocean surface - just below the surface in shallow waters, at the surface, and on coastal land areas, so I need this information to check that the creature's design - senses, communication methods etc - are ball-park plausible. E.g. I don't want to write about how they use echolocation or an electric sense to find prey if it turns out that they would only be effective at a range of millimeters.
I am aiming for a situation where enough light reaches the surface of the planet for photosynthesis to be reasonable (this doesn't have to be earth-like - more efficient pigments than chlorophyll are handwavable), and where light penetrates through the ocean at least far enough to make monochromatic vision useful for communication/close navigation. For sound, echolocation and vocal communication in the oceans (conversation style in a social animal, not cross-ocean whale song) would be nice but not a deal breaker. Shark-like electrosense is just a possibility I'm exploring - if it's feasible life would evolve a way to exploit it.
Background: The planet is (probably - see below) tidally-locked, with a bright-side surface temperature range of approximately 120°C to 170°C. At these temperature ranges, sulfur is liquid - light yellow and relatively thin up to about 157°C, and then dark red and viscous (but less dense) above that. Rivers and oceans will be mostly the yellow form, with dark red viscous patches floating on top at the hottest ocean areas, dark red viscous rivers and lakes on the hottest land masses, and interesting lava-lamp like effects over underwater hot vents or lava flows.
Due to wind currents blowing warm air to the dark side, and ocean currents circulating eastwards around the planet (due to coriolis forces), the dark side temperatures are not too far below (sulfur's) freezing point (113°C). There are thus large regions of solid sulfur 'ice,' but also regions where sulfur remains liquid.
The atmosphere contains sulfur dioxide, and some fluorine compounds (for biological reasons), and probably (but the precise details are not very important) carbon monoxide, carbon dioxide and nitrogen or other gases. The atmosphere will contain sulfur vapor also, due to the liquid sulfur oceans. The atmosphere does not need to be very dense - tidally locked planets can maintain fairly warm dark side temperatures with a relatively thin atmosphere and ocean circulation, and I can handwave it a bit with the very potent greenhouse capability of some fluorine compounds
The planet is host to carbon-based life where plants photosynthesize by absorbing SO2, storing the O, and releasing S. Animals eat the oxygen-containing plant tissues, 'inhale' sulfur, and exhale SO2. Proteins etc are fluorocarbon based, but this is a behind-the-scenes detail.
"Probably tidally locked:" the idea of tidal locking was initially just a way to create areas which would have low humidity (since sulfur vapor strongly absorbs light) yet were near/over oceans: (relatively) steady dry winds blowing over land from the dark side to the light side. I do quite like the idea but am not averse to changing it if it doesn't actually give me the situation I want.
This is my first question after a long period of lurking. Apologies if I've gotten the format wrong in any way (too many questions etc) - if I have, let me know and I'll edit