Detecting vegetation on other planets

Detecting life from reflected light. [Link]

Earth's plant-covered surface absorbs certain frequencies of light, and reflects others. Our vegetation has a very specific spectrum because it absorbs a lot of visible light around 700 nanometers, or the color we see as red. This is called the Vegetation Red Edge (VRE).

By looking at the sunlight that is reflected off of the Earth – Earthshine – the composition of the Earth's surface and atmosphere can be determined. The Earth's light can be analyzed when it is reflected off of the Moon, or from spacecraft distant enough from the Earth to see it as a small disk.

Knowing the composition of the Sun's light, and adjusting for the elements and minerals in the atmosphere and on the surface, there is still between 0-10% of the photons near the red end of the visible spectrum that are missing. The factor needed to explain this photon absorption is the presence of plants, which use the light for photosynthesis

This same method could potentially be used to detect the presence of vegetation on extrasolar planets, proposes Dr. Arnold in a paper titled, Earthshine Observation of Vegetation and Implication for Life Detection on Other Planets published in the October 30th, 2007 edition of the journal Space Science Review.

250 planets found and counting. More chances to find something, particularly as the planets found are smaller and more earth like.