How can my Titan-like cryoplanet have clear skies?

I'm piecing together the biology and ecosystem of a Titan-like cryoplanet. And I want it to have clear or nearly-clear skies instead of Titan's complex hydrocarbon haze, so that my ethane-based lifeforms can use visible light for photosynthesis.

Some planetary info:

• Magnetic field about two thirds the strength of Earth's.
• 120-150 kPa surface pressure.
• Atmospheric composition:
• 90-95% Nitrogen.
• 5-10% Methane or Hydrogen, or a mix.
• 1-4% Ethane (due to evaporation from lakes, seas and oceans).
• Trace amounts (< 1%) of oxygen or some other oxidizing gas or liquid. Emitted by plants as a waste-product.

What compounds could form either naturally or biologically that could function as a transparent UV-absorbing layer? I.e. an ozone layer equivalent.

Is less than 1% oxygen or other oxidizing gas (at 120-150 kPa) sufficient to form an ozone layer able to absorb 90-99% of UV-C and UV-B light? Or are greater percentages of oxygen required?

Could methane naturally react to form transparent UV-C and UV-B absorbing compounds that would be in sufficient concentration to act as an ozone-layer equivalent?

posted over 8 years ago

Laharon‭

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