Why do astronomers search for signs of life on other planets based on living conditions on Earth?

Why do astronomers search for signs of life on other planets when they appear at what’s like on Earth? Couldn't there be entirely different sorts of life on other planets? – Henry, age 13, Somerville, Massachusetts

Have you ever played hide and seek in a brand new place? It's much harder than at home. You only know the apparent hiding places: under the bed, within the closet, behind the couch. The trick is to consider hiding places which you could't even imagine. How do you search in places you never thought could possibly be hiding places?

That is roughly Scientists like me we do after we search for extraterrestrial life; we try to consider latest ways to look for all times. In the meantime, we glance for all times by on the lookout for life like us, because that's what we are able to imagine.

To search something near here

The closest place to search for extraterrestrial life is the planets inside our solar system.

NASA Mission Viking 1 began orbiting Earth's neighboring planet Mars in 1976. The search for all times on Mars was considered one of the mission's most significant scientific questions. The space probe had a lander that would reach the planet's surface and search for all times forms within the dust.

Black and white photo of a rocky floor with struts from the lander's surface sample arm housing
A view of the bottom on the surface of Mars, taken by the Viking 1 lander on August 1, 1976.

Scientists knew that life on Mars could possibly be very different from life on Earth, in order that they didn't search for specific life forms or molecules. Instead, they tried to design experiments to search out out what life does, not what creates it.

Plants and another life forms on Earth, for instance, have photosynthesisa process that uses sunlight and carbon dioxide within the air to generate energy and grow. Viking 1 scientists designed the lander to search for signs of photosynthesis on Mars.

To do that, the lander collected some soil, shone light on it, and took measurements to see if carbon dioxide was passing from the air into the soil. This experiment found no signs of photosynthesis within the Martian soil.

Two other experiments were conducted on the lander to search for evidence of organisms growing in Martian dust. One experiment used carbon dioxide gas, and one other used sugar and amino acid molecules that life forms on Earth wish to eat.

The combination of those three experiments and other measurements led most scientists to agree that there may be probably no life on the surface of Mars, no less than no life that performs photosynthesis or eats sugar. But we still don't know if there may be any evidence of ancient life on Mars, or if there may be any life in any respect deep beneath the surface.

The Viking lander experiments were probably the most direct tests for all times on other planets. Compared to a game of hide-and-seek, these experiments were mainly like looking within the closet: it's a fairly obvious hiding place, but it’s best to look there simply to be certain. Even so, it took a protracted time for scientists to interpret the outcomes.

A bright outburst against a dark field, speckled with smaller stars
At a distance of 4 light years, Proxima Centauri is the closest star to our Sun. Could considered one of its planets host life?
ESA/Hubble and NASA, From

View into the space

The search for all times outside our solar system is even tougher and requires other techniques.

The next Exoplanet – a planet orbiting a star that isn’t our sun – is Proxima Centauri bornand it’s greater than 2 million, million miles (that's 2 followed by 13 zeros) from Earth. These distant worlds are thus far away that scientists won’t send landers to conduct experiments on them for a very long time.

Searching for all times on exoplanets is a bit like playing hide-and-seek in your neighbor's house, but you may only glance through the windows and never go in. You might get lucky and get the appropriate angle to identify someone hiding, but you may't know all of the places you may't see.

Tools just like the latest James Webb Space Telescope can reveal the dimensions of exoplanets, how close they’re to their stars, and maybe the gases of their atmospheres. But that's all. How could we use it to look for all times?

different rainbow colored bands for hydrogen, helium, oxygen, neon and iron
Because elements emit light at specific wavelengths, scientists can use their spectra to find out the composition of a distant planet's atmosphere.
JPL, From

Astronomers have considered looking for life on exoplanets by in the hunt for oxygen. They began this strategy because on Earth, life forms produced many of the oxygen in our atmosphere. Perhaps on one other planet, oxygen was produced by extraterrestrial life.

However, we now have learned that there are other ways to create oxygen that don't require life. So now astronomers aren't just on the lookout for oxygen – they're on the lookout for a planet that has oxygen together with water and other gases like methane and carbon dioxide. Together, these combos could indicate life, as we don't think planets without life would have such combos. But we're still unsure about that!

Searching for all times by on the lookout for these gases is a bit like playing hide and seek behind the sofa. Do we all know that somebody will likely be there? No. But we are able to just glance through the windows and picture that folks are hiding behind sofas. We can try – where else should we glance?

What game are we playing?

There are two big differences between playing hide and seek and looking for aliens.

First, once you play hide and seek, you often know you're fidgeting with another person. We do not know if there are aliens on the market to be found! It's possible that there isn’t a other life on the market, and it's possible that there are aliens right round the corner. Until we discover examples of life aside from our own, we won't understand how common life is within the universe.

View from behind of an astronaut over a ridge in a rocky landscape to buildings
So far no signs of an alien civilization nearby.
janiecbros/E+ via Getty Images

The second difference is that almost all scientists don’t consider that extraterrestrial life is hiding from us; we just haven’t discovered it yet. There are some ideas that more advanced civilizations could avoid being discoveredbut researchers don’t consider this happens in our solar system.

Most astronomers and astrobiologists know that if we only look for all times that resembles life on Earth, we may miss the signs of aliens which might be truly different from them. But truthfully, we've never discovered aliens before, so it's hard to know where to start out. When you don't know what to do, it's often higher to start out somewhere than nowhere.

Searching for all times with experiments just like the Viking lander or for oxygen may not help. But perhaps we'll get lucky. And even when not, we are able to cross a number of obvious possibilities off the list. Then we are able to move on to the harder query of imagining something we've never considered before.

image credit : theconversation.com