资源环境科技发展态势分析平台

The so‐called unknown absorber in the clouds of Venus is an important absorber of solar energy, but its vertical distribution remains poorly quantified. We analyze the 283 and 365‐nm phase curves of the disk‐integrated albedo measured by Akatsuki. Based on our models, we find that the unknown absorber can exist either well‐mixed over the entire upper cloud or within a thin layer. The necessary condition to explain the 365‐nm phase curve is that the unknown absorber must absorb efficiently within the cloud scale height immediately below the cloud top. Using this constraint, we attempt to extract the SO₂ abundance from the 283‐nm phase curve. However we cannot disentangle the absorption by SO₂ and by the unknown absorber. Considering previous SO₂ abundance measurements at mid‐infrared wavelengths, the required absorption coefficient of the unknown absorber at 283 nm must be more than twice that at 365 nm.