The Russian-American Joint Group of Scientists (the Space Research Institute / Roscosmos - NASA) goes on working on a new mission to Venus in the framework of the Russian project Venera D.

Ludmila Zasova, head of the Laboratory for Spectroscopy of Planetary Atmospheres at the Space Research Institute, RAS, explains why Venus should be studied and if there was life there. Besides, she tells what Venus was like a billion years ago and what the mission vehicles are going to do on the planet surface and in its clouds.

- What is the practical interest of the study of Venus?

- Venus is called the twin of the Earth, but its climate is strikingly different from this planet: the temperature on the surface is 470 degrees, due to the greenhouse effect in the atmosphere enveloping Venus like a blanket and consisting mainly of carbon dioxide with the pressure of 95 atmospheres at the surface. For us, Venus is a natural laboratory for studying the greenhouse effect. On Earth, there is a comparable amount of CO2, but thanks to the birth of life, this chemical compound passed into a solid state and found itself mostly hidden in sedimentary rocks of carbonates, in the ocean. When exploring Venus, we will try to figure out how to avoid aggravation of the greenhouse effect on Earth and preserve the conditions suitable for life. So far the greenhouse effect on our planet plays a positive role - it raises the average temperature by + 35 degrees Celsius, otherwise it would have fallen to 20 degrees below zero. This would mean the impossibility of the existence of liquid water and life in today's form. The increasing content of greenhouse gases in the atmosphere, including those from industrial emissions and vehicles may lead to heightening of average temperature on Earth. The evaporation of the World Ocean may intensify the release of carbon dioxide and methane and accelerate this process.

- Are there plans for terraforming Venus? Could there ever be life on that planet?

- Plans for terraforming still remain a fantasy in the lap of the future. The real task is to understand those natural and anthropogenic mechanisms that shape the planet's climate. However, the three planets - Venus, Earth and Mars - are in the so-called habitat zone, that is, at such a distance from the Sun, where liquid water is possible. Thus we cannot rule out the possibility that in the distant past both Venus and Mars might have had life evolving, at least in primitive forms.

Venus might be the first planet in the solar system, where life appeared, that is, earlier than on Earth. Actually, there may be life on Venus even now - in its atmosphere, in clouds at the altitude of 50-60 km, where the temperature and pressure are similar to the terrestrial ones. The clouds consist of 80% sulfuric acid, which means that the drops contain 20% water. And we know a number of terrestrial bacteria that can live in a concentrated acid solution. For example, Helicobacter Pylori, which lives in the hydrochloric acid of man’s stomach.

 - If Venus once looked like Earth, what happened to it?

 - The issue remains open. During the last billion years, more precisely, from 500 million to 1 billion years ago, there were powerful volcanic eruptions on Venus; as a result, the surface was covered with basaltic lava. Only individual mountainous areas of the surface, the tesserae, which may store the history of the ancient processes, were left untouched. A study of the surface composition in tessera might help to understand the history of Venus before eruptions: to check, for example, whether there are minerals such as granites that are formed only in the presence of water.

 - What will the mission Venus D be like?

 - Orbital and landing vehicles are the basis of the mission. The landing vehicle is designed for two hours of operation on the surface of Venus only, but this is enough to perform basic research with scientific instruments on board. The most modern scientific instruments will be installed in the pressure shell onboard; in particular, it will be equipped with a device for taking atmosphere and ground samples to study on board. There will be several cameras, including panoramic ones, and a camera with high resolution of up to 0.1 mm.

Venus is covered with a layer of clouds 20 km thick, and for understanding many of the key issues of Venus, direct measurements in its clouds, in the atmosphere and on the surface are necessary. The orbiter is designed for at least three years of active operation, but we hope that it will work much longer. Various spectrometers will be installed on this module to study the dynamics, atmospheric superrotation, atmospheric composition, clouds, the nature of the ultraviolet absorber, the surrounding plasma, etc.