Overview

Our species has evolved an intense and nearly insatiable curiosity. When observing the sky, we naturally wonder if we are the only beings that populate this vast and colossal cosmos. In recent decades, experts developed a number of different methods that could allow them to identify signs of biological activity beyond Earth. Preliminary results involving biomarkers are staggeringly promising, as scientists have discovered numerous signs of organic molecules on other worlds. 

The science and other stuff to know

Today, experts search for signs of life on other planets using a host of different methods. Peer reviewed studies evaluating these methods indicate that each has its own unique pros and cons, but that no one has any clear advantage over the others. 

However, most modern methods typically involve the identification of biomarkers, which are chemical phenomena that typically result from biological activity. When scientists, for example, detect molecular oxygen (O2) or ozone (O3) present in the atmosphere of an alien planet, the extraterrestrial life alarm is activated. Why? Because the only well-known mechanisms for synthesizing these compounds on Earth are from biological disposal. 

As Physics Professor Brad Carter and colleagues put it, “Without the constant resupply coming from life, the free oxygen in the atmosphere would largely disappear.” In short, an abundance of oxygen may mean there’s an abundance of life. 

Of course, oxygen doesn’t guarantee that a planet is inhabited. However, by studying how these levels vary over time, NASA-funded research found that scientists can get a pretty good idea about whether life exists on the world. 

In 2013, research published in Nature found that Mars had an oxygen-rich atmosphere some four billion years ago. Although the Red Planet may be a desert world today, this evidence indicates that the planet may have once been hospitable to life. “It is likely that the ‘Red Planet’ was wet, warm, and rusty billions of years before Earth’s atmosphere became oxygen-rich,” said Lead scientist Professor Bernard Wood of Oxford University said.

Of course, oxygen and ozone are far from the only biomarkers, and they are far from the only biomarkers we’ve detected. 

In November 2020, an article published in Nature Astronomy reported the detection of phosphine, another biomarker, in the atmosphere of our neighbor Venus. More recent studies have found methane, which is also an organic material, in samples taken by the Curiosity robot on Mars. 

So what?

Beyond the philosophical interest that we humans have in determining whether or not we are alone in the cosmos, the quest to identify signs of life in other parts of the universe helps protect human life. It may sound like a dramatic statement, but a lot of this innovation ends up creating spinoff technologies that greatly benefit humanity. By investing in the search for alien life we are, in some ways, investing in our own future. 

What’s next?

It is necessary to continue investing financial and intellectual resources in the improvement of biomarker detection instruments and methods, as well as other techniques capable of giving indications of biological activity outside home. We must also build increasingly sophisticated instruments that can transmit and receive signals from other potential civilizations.

There are a number of organizations that let you contribute to this mission.