On December 15, 1970, Venera 7 set down on Venus, completing the first ever soft landing of a probe on another planet. The first images of the planet’s surface were transmitted to Earth on October 22, 1975 by Venera 9. Up until 1985 eight more landings followed. Since then, interest has waned. To date, there have been only a further three missions with Venus as their primary destination, none of which landed on the surface of the planet. Attention has shifted away from Venus in favor of Mars. Even the establishment of a colony on Mars is being seriously considered. By contrast, the possibility of a settlement on Venus is not being discussed at all. In view of the extreme conditions that prevail on Venus, most scientists doubt that there is life on Earth’s closest neighbor. Surface temperatures of well over 400 degrees Celsius, an atmosphere that is toxic to terrestrial life and an extremely high atmospheric pressure suggest that Venus is not a hospitable place for life of any kind. However, the possibility of life existing on Venus cannot be entirely ruled out according to Dr. Klaus Slenzka, Head of Life Sciences at OHB. After all, life on Earth has shown remarkable adaptability in the course of its genesis.
Mr. Slenzka, how likely is it for life to exist on such an inhospitable planet as Venus?
Before speculating on the probability of life on other planets, we must realize that everything we think we know about life is based on research into life on Earth. If we consider the conditions on Venus in the light of our terrestrial ideas of an environment capable of supporting life, the only conclusion that we can draw is that life on Venus is not possible. Yet, that is not the right approach. We do not want to know whether the forms of life found on Earth could survive on Venus but whether life may have developed on this planet of its own accord. And if you look at the development of life on Earth, this is not such an absurd idea.
It is important to remember that life on Earth has not always existed in its present form. The conditions that we find on Earth today are very different to those in which the earliest forms of life emerged 3.8 billion years ago.
How did they differ?
Take the composition of the atmosphere, for example. The vast majority of life found on Earth today needs oxygen to survive. However, the atmosphere has only existed in its current composition for about 350 million years. Before that, it consisted primarily of carbon dioxide, methane and ammonia. When the photosynthetic activity of the earliest forms of life caused oxygen to accumulate in the air, this led to the first major mass extinction in the history of Earth. For many of the organisms that had arisen under anaerobic conditions, the growing oxygen content in the atmosphere had the same effect as an accumulation of toxic gas. Organisms that had found ways of using oxygen to generate energy then occupied the ecological niches that became free.
What does this mean for the search for life on other planets?
We tend to be looking for a second Earth in our search for traces of life. Yet, this is absurd. Why should it be that biology on Earth is the measure of all things? True, the number of chemical elements occurring in the universe and, hence, the potential building blocks for life is limited. But does that also mean that life on all planets must be based on carbon just because that is the case on Earth? In no scientific definition of life that I know of is this a condition. And in any case who says that planet Earth is not still evolving? It is possible that in a few 100 millionyears from now the conditions on Earth will be very similar to those currently found on Venus, but it will still hold life that has adapted to the changes in the course of evolution.
If life on other planets is potentially fundamentally different from life on Earth, what possibilities do we have for detecting it as such?
There are a number of key physical and chemical characteristics that all living organisms share.These include the existence of an external boundary to the environment, the ability to grow and reproduce and the evolutionary ability to adapt to certain environmental conditions.
Can we determine from the surface of Earth whether there is life on Venus?
No, in order to look for life on Venus, we must carry out investigations in-situ.
What form could life take on Venus?
If we do actually find life on Venus, it will probably be in the form of unicellular organisms or simple multicellular organisms. Spectral analyses of the cloud layers of Venus suggest the presence of such organisms in the atmosphere. Until 700 million years ago, higher life forms could have existed on the surface of Venus. Simulations carried out by NASA’s Goddard Institute for Space Studies have shown that Venus may have been covered by oceans with mild temperatures for two to three billion years. This time span would have allowed the emergence of higher forms of life. However, they are unlikely to have survived the onset of the self-reinforcing greenhouse effect and the resulting conditions that we find on Venus today.
In 2012, the images of the Soviet Venera missions were re-evaluated for publication in the International Journal of Astronomy and Astrophysics, and the author claims to have discovered structures in the images that indicate the existence of higher forms of life on Venus. What is your take on that?
When you look at the pictures, it is important not to forget that they were taken on the surface of Venus, where technical equipment survives only a few minutes to a couple of hours. It is therefore conceivable that the structures described are actually artifacts. Besides, the names of the objects make me wonder. Mention is made of leaves, an owl and a scorpion, among other things. Although the author points out that the names are based purely on the external form of the objects, analogies to earthly forms of life are repeatedly used in the text. All in all, the information loses its scientific value as a result of this. A different wording would certainly have been more appropriate here.
If we were to actually discover life on Venus, would that also have any benefit for Earth?
Yes, absolutely. If we assume that Venus has progressed further than Earth in its evolutionary history, we can possibly gain an idea of what lies ahead for our home planet on the basis of what we find on Venus today. So far, our knowledge of Venus is more than rudimentary. One major challenge, however, is to engineer equipment that is able to withstand conditions on Venus over an extended period of time. Long-term observations are necessary to determine whether there is life on Venus. However, these observations should not concentrate solely on searching for carbon-based organisms but rather on looking for the key characteristics of life, such as changes in mass through growth and reproduction. It is possible that these key characteristics will lead us to completely new aspects of life that we have previously not encountered on Earth. That would be a sensation that would surely have serious implications for our understanding of biology on Earth.