Astronomy and Astrobiology: Life Beyond our Home on Earth


Astronomy is a science that uses physics, chemistry, and mathematics to measure, predict, and work on getting a deeper and more accurate understanding of the materials that celestial objects and other phenomena are made up of, the distance between them, and what causes their behavior. Astronomers examine moons, planets, comets, stars, galaxies, and the universe itself in their search for answers.

 Astrobiologists look at our universe as well, but they examine life on earth and other planets, and they make predictions regarding its distribution in the future. They seek to find ways to determine if we are truly alone in this universe.


What is Life and What Does it Need?

The dictionary definition of life is “the condition that distinguishes animals and plants from inorganic matter, including the capacity for growth, reproduction, functional activity, and continual change preceding death.” In other words, people, animals, plants, fungi, and bacteria are all forms of life; while rocks, gases, and sand are not.

All living organisms:

  • Grow
  • Reproduce
  • Are made up of chemicals
  • Have a response to their environment

In order to thrive, life needs to have water, air, chemicals, and a source of energy such as the food we eat.

  • Water – The majority of organisms are primarily composed of water, and humans are no exception to the rule.
  • Air – Animals require oxygen from the air to survive, and plants require the carbon dioxide that air also carries.
  • Chemicals/elements – Without carbon, hydrogen, nitrogen, and oxygen we would not have the building blocks needed to make proteins and nucleic acids; and without those, we would not have what is needed to replicate genetic code.
  • Energy – Energy sources may include other organisms (such as when carnivores eat meat or herbivores eat plants), other materials, or light (such as in photosynthesis by a plant).


How Astronomers Search for Life

One of the first thing astronomers do is look for evidence of oxygen and water on a planet to see if it can sustain life as we understand it. In addition to that, they consider if the sun that a planet is near is one that can help to sustain life, and they consider things such as the planet’s surface temperature and climate.

They also look for chemical traces and other evidence left behind by life. If a planet is close enough, they may send probes there to collect samples and get close-up photographs to study. When they look for life, they are not simply looking for large animals of human-like aliens, but also microorganisms.

Scientists are also using radio signals. Not only have they sent radio signals into space in the hopes of getting a response, but they are also listening for signals on a wide range of radio frequencies.

Additionally, they use photos taken via powerful telescopes to determine if there could be structures, such our own buildings and infrastructure, on other planets.


Search for Life Beyond Earth

It’s only natural that we would look to the stars and wonder about what – or who – might be out there. In astrobiology, we begin that search in earnest at the next planet over, and then further out into our own galaxy, and then even further than that.

Life on Mars

Our search for life outside of our own planet begins on the next planet over – Mars. It is somewhat similar in its proximity to the sun, and we have discovered that there is water on the planet, although the vast majority of it is currently in the form of ice. The first probe to fly over Mars was the Mariner 4, and it reached the planet in July 1965.


Life in the Outer Solar System

Jupiter, Saturn, Uranus, Neptune, and Pluto hold many secrets – but so far, none of the ones we have discovered include life. The harsh conditions, poisonous gases, catastrophic storms, and cold conditions on these planets seem to make them an unlikely place for life to flourish. However, that hasn’t stopped scientists from looking even further and reaching outside of our galaxy in their explorations.


Life Beyond Our Solar System

Is there life beyond our solar system? It seems likely. There are other planets out there that come very close to matching the conditions of our own. In a wide universe with many chances for life, it seems unlikely that we would be the only planet with life in the form of plants, animals, or even microorganisms.


Astronomy and Astrobiology Resource for Educators

The UCI Observatory, Department of Physics & Astronomy has a wide range of useful sources of astronomy information on the internet on their website: Useful astronomy information for parents, teachers, and the public.

The University of Colorado Boulder also has an extensive list of astronomy resources on their site: Astronomy related links.

NASA has some fun and interesting hands-on projects for educators: Astrobiology in your classroom…life on earth and elsewhere?