Life on… Venus?
Venus has been in the news recently, and for rather unexpected reasons. Life - or rather the evidence of life - may have been found by researchers.
When searching for extra-terrestrial life remotely, scientists rely on what are effectively fingerprints of the signs of life on a planet. These can be a variety of different chemical signals which show that something organic is producing an effect that cannot be replicated by any other means. Simple biomarkers might be an oxygen rich atmosphere, or evidence of liquid water. One criterion for a good biomarker is that it is not in a state of equilibrium - that means that the chemical would disappear in a short time interval without life constantly replenishing it.
Recently, led by universities in the UK, a group of scientists began a search using the biomarker phosphine. On Earth this rare chemical is only found in situations where it has been generated by life (either bacteria or higher life forms). The group requested time on some of the world’s largest radio telescopes and asked for them to examine the spectra from the atmosphere of Venus. To their amazement, a spectrographic signal of phosphine was found.
After scrupulous analysis of their results, and to disprove the chance of the phosphine being produced by inorganic means the researchers published their findings. The group propose that phosphine might be being produced in the Venusian atmosphere by something akin to microbes that have an exotic lifecycle. The putative ‘microbes’ may float high in the sulphuric acid clouds and live out their active lives, then when winds blow them back down to the surface of the planet, they hibernate to survive the crushing pressures and high temperatures.
Now of course this is incredibly exciting news, but many scientists are cautioning that it may not be evidence of life on Venus. There may be some unknown chemical process producing the phosphine. Nonetheless, this result will certainly invigorate proposed missions to Venus, and perhaps Venus will become as much of a target for future exploration as Mars is today.
Imaging VenusSo, considering Venus is in the news, perhaps now is the time to take up the challenge of imaging what is a somewhat neglected member of the solar system. Due to the fact that the planet is shrouded in almost impenetrable clouds, it is generally ignored by planetary imagers. But this view is beginning to change as there are certain techniques and technologies that enable us to lift the veil and image detail in the clouds and the surface.
What has Venus got going for it? Well for starters, Venus is the third brightest object in the sky after the Sun and Moon, and is one of the most beautiful sights in the night sky. The brilliant Morning or Evening Star can be seen during normal waking hours, rather than in the small hours of the night which also makes observing easy.
Venus seen without specialised filters will appear completely and dazzlingly white, but even so it is still an impressive target for visual and photographic study. As it is relatively close to the Earth and also closer to the Sun than the Earth, it shows large and easily visible phases. Imaging under high magnification displays these phases well with a small telescope.
Filters - In the last few years amateur astronomers have been able to access filters that previously would have only been available to professionals.
Near Infrared Filters for Surface ImagingWhen Venus presents a very narrow crescent it also appears with its largest apparent diameter. Along with the opportunity for dramatic photographs of the large crescent phase there exists the chance of imaging the surface and lower cloud levels using near infra-red filters. This is due to the fact of an atmospheric ‘window’ in the 1 micron wavelength part of the spectrum where the clouds can effectively be seen through.
To enable the best results, along with specific filters the telescope needs to have the right type of optical coatings and have a large diameter. The webcam or planetary camera used also needs to be sensitive to this particular part of the spectrum. Images have been captured by amateurs that do show hints of surface features, and this could be a really exciting challenge to replicate.
Ultra Violet for Atmospheric Imaging
Rather than trying to capture surface detail, another option is to view the atmosphere and clouds in more detail. This can be achieved with ultraviolet pass filters in the 350 nanometer band, which are now enabling amateurs to image detail in the atmosphere of Venus.
An alternative to the expensive dedicated 350nm UV filter is to use a much more inexpensive violet visible light filter and this can produce effective results as well.
So perhaps Mars now has competition… both in the search for extra-terrestrial life and as the closest interesting target for planetary imagers!