Scientists should look for this when they search for planets with life

Researchers will be looking for habitable planets, but they stress that this is not an exit strategy:

-There is no planet B. If we find other habitable planets, it must be emphasized that we will not move there.

This is what the leader said Planetary Habitat Center (PHAB) Trond Torsvik when the center was recently opened. He is a professor at the University of Oslo.

On the other hand, the goal is to understand the conditions that enable life to arise and flourish. Perhaps you will also find such planets.

Planets orbiting stars other than our star are called exoplanets. Today, about 5,500 planets of this type have been discovered. The first exoplanet was discovered by Didier Queloz and Michel Mayor in 1995. They received the Nobel Prize for it in 2019. Queloz was invited to attend the center’s opening.

They should look for this

– The possibility of life on other planets has fascinated humanity for a long time. How did we get here, why are we here, and are we alone? “These are questions we are trying to answer, but we are focusing on what makes the planet habitable,” Professor Stephanie Werner said in her opening lecture.

When researchers look for habitability, there is one factor in particular that is important, Werner said:

The presence of liquid water on an exoplanet depends on temperature, which in turn depends on several things: the distance from the sun it orbits, the sun’s activity and size, and the atmosphere and activity inside the exoplanet.

One of the things that has been studied is the so-called habitable zone. This is a certain distance from the Sun where there are comfortable conditions for life.

– Today the Earth is in the habitable zone. What constitutes a habitable area changes over time. Earlier it was Venus that was in the habitable zone. And in the future it will be Mars. We know that habitability depends on time. So it’s important to be able to say something about the age of the planet and the solar system, explains Werner.

The age of exoplanets can become challenging, because the planets to be examined are so far away. In addition, these solar systems may be different from ours. Therefore, it is not easy to compare the processes that formed the solar system.

We’ll look at observations of exoplanets and look at what we know about planetary evolution to understand what kind of atmosphere we can expect. Next, we’ll look at how habitable the planet is. How do we do that? We need mass, radius and mass distribution in the planet, Werner summarizes.

A habitable planet must have an atmosphere

The atmosphere surrounding Earth today makes it possible to sustain life here. It retains heat with the help of greenhouse gases and protects us from radiation.

In addition, our atmosphere is made of oxygen. It is important for multicellular organisms. Without oxygen, we would still be bacteria. However, Earth’s atmosphere was not always hospitable.

Werner explains that the atmospheres around Venus, Earth and Mars were quite similar when the planets formed.

– The first atmosphere during the formation of the planet was probably very similar to the formation of the Sun, that is, consisting of hydrogen and helium. This atmosphere dissipated very quickly. The next part consists of gases from volcanoes and magma oceans. It produced an atmosphere consisting of carbon dioxide₂, especially. After the appearance of cyanobacteria that invented photosynthesis, oxygen gradually increased in the Earth’s atmosphere, Werner explains.

In addition, planets that are very hot or very cold can have atmospheres that “evaporate” or “freeze”:

– When we look at many planets that we think are very hot, we don’t expect to see atmospheres. Then we have some planets that are so cold that the atmosphere must condense on the surface, Werner says.

When scientists want to understand a planet, it’s important to understand the type of atmosphere surrounding it and the things that affect the atmosphere.

On Earth, it is life itself that ensures the presence of oxygen in the atmosphere, but there are other gases that can also be signs of life. One of them is the phosphine molecule.

Oxygen and water are not the only signs of life

Phosphine has been found in the atmosphere of Venus, and it has been speculated whether this might mean life exists or has already existed there. On Earth, phosphine is produced by living organisms, but it turns out that conditions on Venus are so different that it is possible for phosphine to occur without life as well.

Werner says such discoveries often generate big headlines without necessarily:

-We have an exoplanet with an atmosphere that we can observe. It is called K2-18 B. It was observed by the Hubble Telescope. Then the headline was that this could be a habitable super-Earth. A few years later, the planet was observed using the James Webb Space Telescope and other instruments. We now believe that this is not a super-Earth, but a single Earth Planet Hessian“Werner says.

Classifying the planet as a Hessian planet means that it has a hydrogen-containing atmosphere and that there is likely liquid water there.

Could our magnetic field be the basis of life on Earth?

It has long been assumed that liquid water and an atmosphere are essential conditions for life. It is perhaps less well known that a magnetic field may have contributed to making Earth a habitable planet.

Anyway, this is one of the questions the researchers asked themselves: What role does the magnetic field play? What is the role of the moon? What role does plate tectonics play?

All of these factors are believed to influence life on Earth, but it is not known to what extent they influence, and which factors are decisive. The researchers will therefore investigate how biodiversity on Earth has been affected over the past 750 million years.

– During this period, the Earth experienced radical changes in its climate. The Earth, for example, was a snow globe. We therefore ask how these changes have affected biodiversity, Werner explains.

One way to see what factors are at play is to compare with other planets. Mars has a number of features in common with Earth:

Mars contains traces of liquid water because we saw clay minerals and river deltas. We have also seen that Mars had a magnetic field. We don’t know what happened, but the magnetic field disappeared. Then the atmosphere disappeared too. Mars may have had an environment suitable for life, but it ended up becoming an icy desert, Werner explains.

How do you see the planet?

In addition to understanding how planets form and evolve, finding them is part of the problem.

Some planets can be seen directly, but they must be very large and at the perfect angle for a telescope.

In addition, planets can be seen when they pass in front of their sun, but they also have to be at the right angle to the telescope – which doesn’t happen very often. To illustrate this, Werner included a picture of Venus:

– This is Venus in front of our sun in 2012. The next time we can see it from Earth will be in 2117, so these are very rare events. We have to see it from the right angle in order to see it,” she explains.

It is possible that there are many planets, but it is not certain that we can see them.

The most common ways to see planets are to measure changes in the star’s speed and changes in the light emitted by the star. Both star movements and changes in light can be caused by planets.

The fact that there are many things to do to see the planet may be an explanation for the fact that the first exoplanet was only confirmed about 30 years ago. Nobel Prize winner Didier Queloz explains this discovery as follows:

– We used a technique that wasn’t really supposed to work, but it turned out to work surprisingly well given that there are so many planets, he said.

He further explains that the most amazing thing is that there is no planet similar to Earth, which has the same location as Earth.

There is one good reason for this: our technology cannot see such planets.