The places where scientists look for extraterrestrial life – 03/24/2024 – Science

It’s very easy to get excited when it comes to alien life.

The prospect of finding life on other planets has formed a large part of our culture and continues to inspire books, TV shows, films and, of course, strange conspiracy theories.

But alongside the fantastical visions of little green men, there’s a real search for alien life going on right now – and it’s not controversial ideas, nor is it some kind of pseudoscience. It is a systematic process led by scientists, who hope to obtain results within a decade.

In fact, there are several searches for alien life underway. On Mars, for example, a mobile robot – Perseverance – is collecting samples that could determine whether life once existed on the red planet.

Probes are visiting some of the icy moons in our Solar System, looking for signs of habitability. Astronomers are also beginning to analyze the atmospheres of planets outside our Solar System, looking for elemental cocktails that betray alien life.

And, of course, our skeptical eyes and ears remain alert for signs of any intelligent civilization that makes contact, whether on purpose or accidentally.

“I think that, within 10 years, we will have some evidence indicating whether there is something organic on a nearby planet”, says British Royal Astronomer Lord Martin Rees. “I think we’re really [a ponto de encontrar algo].”

Mars

Alien life, if it exists, is not easily discovered.

The first attempts to search for extraterrestrial intelligence began in the mid-20th century, with Seti Project astronomers searching for radio signals from other planets, without success.

In the late 19th century, Mars was believed to have rivers and canals teeming with life. But the planet turned out to be a barren and basically dry land. And the planets orbiting other stars are so small that finding them was difficult enough, let alone learning much about them.

In the search for extraterrestrial life, we need to fine-tune our search and prepare for the possibility that any initial detection may be something small, like evidence of microbes or chemical tracers in a distant atmosphere.

Compared to the Hollywood vision, the first contacts with extraterrestrial life may seem disappointing, but eventual conclusive evidence of the existence of life beyond the borders of our planet would still fundamentally alter the view of our place in the Universe.

Currently, Mars is, without a doubt, the most popular destination for the search for life in our Solar System. After all, we know that the planet was probably wet and possibly habitable billions of years ago, with seas and lakes on its surface.

Scientists recently discovered fascinating indications that there may still be liquid water on Mars, hidden beneath the ice sheet in the planet’s south.

Right now, NASA’s Perseverance roving robot is taking samples from the dry bed of what is believed to have once been a lake. It is called Jezero crater, a short distance from the Martian equator, in the northern hemisphere.

The plan is to collect dozens of samples and bring them to Earth in the early 2030s, in a mission called Mars Sample Return. They can then be thoroughly analyzed, looking for signs of life.

This mission currently faces difficulties, as the return still needs to obtain funding. But, if the samples manage to leave the red planet, we will have a great scientific wealth in our hands.

Planetary scientist Susanne Schwenzer, from the Open University of the United Kingdom and a member of the scientific team for the Mars Sample Return project, says that the presence of life on Mars in the past may have left its fingerprint on the planet’s rocks and water.

“When you have a life, everything looks very different,” she says. “If we have the samples from Mars, we can analyze their smallest details to study these processes.”

It is possible that some of the samples may even contain fossilized microbes within the rocks.

“As a scientist, I wouldn’t have spent my life on this if I didn’t have hope that we have a good chance of finding something,” explains Schwenzer. “I hope we find something, but I can’t make predictions.”

The icy moons

Even if signs of life are detected on Mars, this would not be unequivocal proof that alien life exists everywhere in the Universe.

We know that Mars and Earth shared material early in their history. This means that the two planets may also have shared the genesis of life.

To find evidence of a real second genesis, that is, proof that life arose for a second time on another world, independently, scientists are searching the icy moons of the Solar System, such as the satellites Europa (Jupiter) and Enceladus (Saturn). They believe that both have vast oceans beneath their frozen surfaces.

“If we discover life on the icy moons, it will certainly be a different genesis from life on Earth,” explains Schwenzer.

NASA is expected to launch a spacecraft called Europa Clipper towards Europe in October. It follows the launch of the European Juice spacecraft in April 2023.

Scheduled to arrive in 2030 and 2031, the two spacecraft will probably not detect life on Europa. But they will study the extent of its ocean and define the scenario for a future mission, which could try to excavate the ice sheet (as proposed by NASA in the Europa Lander project, still in its initial phase), or fly through plumes that can be ejected through the oceans of the moons into space, searching for signs of life.

Putting a machine in the ocean of one of these worlds is actually a “100-year problem”, says astronomer Britney Schmidt, from Cornell University, in the United States. This is due to the difficulties of crossing ice several kilometers thick.

But “entering the ice layer and interacting with the liquids is something we could do” in a shorter period of time, according to her.

“It’s the type of mission I would like to see happen. Our group is developing instruments and technologies, so we already know what to do when we get there,” she says.

Exoplanets

If you’re not prepared to wait for 100 years, you might want to take a look at other solar systems.

We now know of more than 5,500 planets that orbit other stars – so-called exoplanets – and new discoveries continue to appear every day.

With the immense power of new telescopes, particularly the James Webb Space Telescope (JWST), astronomers are beginning to examine some of these planets in beautiful detail.

They are using JWST particularly to see if they can find out what gases are present on some rocky Earth-like exoplanets.

James Webb was not intended to analyze exoplanets when it was initially designed at the turn of the century. But, from then on, he received the new task of studying these worlds. After all, the JWST is the largest space telescope in history and the best machine we have for this mission.

James Webb cannot study Earth-like worlds orbiting stars like our Sun. The image of these planets is simply obscured by their bright stars and even JWST cannot analyze them.

This will require a more advanced telescope, such as NASA’s Habitable Worlds Observatory, scheduled for launch in the 2040s.

But James Webb can study planets that orbit small stars, called red dwarfs. And right now, he’s testing his capabilities with a fascinating solar system called TRAPPIST-1, which includes seven Earth-sized worlds.

At least three of these planets orbit in the star’s habitable zone, where liquid water and life may exist.

The first step is for astronomers to confirm whether these planets have an atmosphere. Research to determine their presence through the JWST is currently underway and results are expected later this year or in 2025.

Initial results demonstrated that the planet with the innermost orbit probably does not have the atmosphere necessary for life. But if we can find atmospheres on the other planets in the TRAPPIST-1 system, it will be a monumental discovery, according to astrophysicist Jessie Christiansen, from NASA’s Exoplanet Science Institute at the California Institute of Technology, in the United States.

“The next 20 years of exoplanet research will depend on this result,” according to her. “If the red dwarf planets have atmospheres, we will point all of Earth’s telescopes toward those planets to try to see something.”

If we manage to find atmospheres on these planets, it will be James Webb’s turn to look for signs of biosignatures that could indicate the existence of life.

“We will look for the chemistry of the imbalance,” explains Christiansen. “You can produce carbon dioxide, methane and water in [qualquer] planet. But finding them in proportions that can’t be maintained naturally is the point at which you start to say there is biology involved.”

Telescopes of the future, such as the Habitable Worlds Observatory and a European project called Life, will attempt to perform the same analysis in search of Earth-like planets that orbit stars like our Sun.

“The guiding planetary class will be rocky planets in the habitable zone”, according to astrophysicist Sascha Quanz, from the Federal Institute of Technology (ETH, its German acronym) in Zurich, Switzerland. He is the head of the Life program.

And so the search for intelligent life continues.

The next steps

Astronomer Jason Wright, from Pennsylvania State University, in the United States, indicates that the first fruits have already been harvested.

Observations of radio waves have shown that, up to about 100 light-years from Earth, there are “apparently no” powerful lighthouses pointed in our direction. Now, programs like the American Breakthrough Listen are turning their research to greater distances.

They look for radio signals emitted from planets further away in our galaxy – and are even starting to look for accidental communications leaks like those we have today on Earth, but coming from other planets.

Upcoming telescopes, particularly a huge new radio telescope due to open in 2028 called the Square Kilometer Array (an array of thousands of radio antennas spread across two continents), are expected to significantly expand this research.

“It’s really exciting,” says Wright. But even with modern radio telescopes, the first detection could come “at any time”, according to him.

If we do find evidence of alien life, whether in our Solar System, on an exoplanet or from an intelligent civilization, it probably won’t be an extraordinary event. Most likely it will be a gradual process until we reach the point where life seems like the most plausible explanation.

“The more information you have, the closer you are to a position to eliminate false positives,” says Quanz.

Therefore, the discovery of extraterrestrial life may not be a single defined moment. And how the public will react to that possibility is an interesting question, according to Rees.

“If it is something preliminary, scientists should make this point clear,” he says. “We hope this is manifested in newspaper reports.”

Recent examples include the detection of phosphine on Venus and dimethyl sulfide on an exoplanet – two possible biological signals that have generated intense debate and remain extremely uncertain.

Another possibility also remains: that none of these searches yield any results. This will also be an interesting scientific result, which would indicate that alien life, if it exists, is not common in the Universe.

“A null result would reveal something fundamentally important” about life, according to Quanz. “Perhaps it is very rare.”

This text was originally published here.