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Comic book scene of three rovers on red rocks. Leftmost rover burrows into rock with a metalic tool, center rover explores a large hole, and rightmost rover emits red laser light onto a rock in the foreground.

7.2. How do we explore within our own Solar System for signs of life?

A core learning question from the Astrobiology Learning Progressions

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7.1. What is a biosignature?

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7.3. How do we discover worlds around other stars?

Grades K-2 or Adult Naive Learner

We are all born scientists. We are curious. We look for patterns. We compare and contrast new things to our past experiences. For example, we all know our own homes well. We know what it looks like, sounds like, and feels like. When we visit a new place our minds naturally begin to compare and contrast to what we know. If you have ever changed homes, then you know we spend a lot of time and thought on what is similar and what is different. When we do this, we are using our scientific mind. Explorers in new lands do this in much the same way. Science is a way of thinking and learning.

Portrait photo of Comic book scene of three rovers on red rocks. Leftmost rover burrows into rock with a metalic tool, center rover explores a large hole, and rightmost rover emits red laser light onto a rock in the foreground.
Rovers sent to Mars have payload instruments capable of analyzing the surface and shallow subsurface to search for signs of life. Payload instrumentscanuselaserspectroscopy and other analytical techniquestoget chemicalsignaturesofpossible biosignatures in rock and soil.
NASA/Aaron Gronstal

Grades 3-5 or Adult Emerging Learner

We can learn about our world by using our senses such as sight, hearing, smelling, and touching. We also investigate using measurement tools such as rulers and by using tools that enhance our senses like telescopes and microscopes. The type of tool we choose depends on what we want to learn about and how hard it is to investigate. For example, if we want to learn about a fish here on Earth, we might watch them, count them, and even catch and weigh them. When we think about learning more about our solar system, we must consider what we want to learn and what tools we could use. Also, we have to keep in mind getting to other places in our solar system can be hard because other planets are really far away.

So far, we’ve only sent humans to the Moon and back, and we’ve been using robots to explore other planets. Some of our spacecraft fly past a planet and take pictures. Other spacecraft have gone into orbit around other planets and stayed there to learn more. We’ve even sent out some robots that have landed on other worlds to explore. We send along special tools on these spacecraft that send information back to Earth so we can study those other worlds. There is much to learn about the other worlds in our solar system. Some places we think might even have living things on them. For us to find out, we need to keep exploring and sending our spacecraft out to these other worlds. We all think like scientists when we ask questions, investigate, and compare and contrast new things we find to things we already know. Similarly, the scientists who are looking for possible signs of life in other places in our solar system will compare and contrast those place with what we find here on Earth. In order to understand more of the nature of our universe we must continue to explore, use our senses and instruments, and consider how similar and different these places are. Then, we have to ask, “Why?”

Portrait photo of Comic book scene of three rovers on red rocks. Leftmost rover burrows into rock with a metalic tool, center rover explores a large hole, and rightmost rover emits red laser light onto a rock in the foreground.
Rovers sent to Mars have payload instruments capable of analyzing the surface and shallow subsurface to search for signs of life. Payload instrumentscanuselaserspectroscopy and other analytical techniquestoget chemicalsignaturesofpossible biosignatures in rock and soil.
NASA/Aaron Gronstal

Grades 6-8 or Adult Building Learner

Do you think Earth is the only place in our solar system that has life? Even though we haven’t discovered life anywhere else in our own solar system yet, there are many people who wonder if there was ever life, or might even be life right now, on other worlds right here around our own star. If there are some living things on maybe Mars or Enceladus, in the atmosphere of Venus or on a comet, how would we find it? We humans can learn a lot by interacting with the world and using our own senses to make discoveries. It is pretty hard to physically send humans to other worlds to explore. So far, the furthest humans have ever traveled away from our planet is just beyond the Moon. In 1970, the crew of Apollo 13 set the current record when they swung around the Moon at 248,655 miles (400,171 km) away from Earth. For us to send humans to worlds like Mars and the moons of the outer solar system, it’s going to take some time. In the meantime, we send out robotic spacecraft as explorers for us. Sometimes we send spacecraft that will fly by another world and collect information. They may even go into orbit around the planet or other object in order to study it. We also send robots that can land on the surface in order to look at these other worlds close-up!

When we design our spacecraft, we have to consider the kinds of instruments that we want to send along. They can include cameras and a variety of tools for studying the chemical and physical environments of the worlds the spacecraft are exploring. The instruments that we put on the spacecraft will depend on the type of spacecraft it is and if it’s going into orbit around a planet or landing and drive around, for instance, on the goals of the mission, and where it’s going. Because of the spacecraft that have observed Europa, a moon of Jupiter, we now know this moon is a world with an icy shell on top of a deep liquid water ocean. Our first images of Europa up close came from the spacecraft Pioneer 10 and 11 and Voyager 2 in the 1970s. With Voyager, we saw for the first time that the icy crust of Europa had dark streaked lines all over it. These lines (which we refer to as “lineae”) were the first indication that the icy surface could be cracked and might have an ocean below. The Galileo spacecraft, which spent 14 years studying Jupiter and its moons (from 1995 to 2003), had an instrument onboard for measuring magnetism. If you’ve ever put one magnet close to another, you’ve seen the effects of magnetism. We have tools that allow us to measure the effects of magnetism and they’re called “magnetometers”. In fact, a compass is actually a very simple type of magnetometer. Just as we can use a compass to tell us which way is north on Earth, a magnetometer can tell us about the magnetism coming from a planet or a moon. The magnetometer on Galileo showed us that Europa must have a salty liquid water ocean down below its surface. Can you think of why a liquid water ocean could be so important when looking for life?

On Earth, hydrothermal vents are a source of heat and energy on the ocean floor and have developed ecosystems around them where sunlight isn’t needed for energy. Could there be hydrothermal vent ecosystems within the ocean of Europa? With future spacecraft, we’ll fly by and even orbit Europa, taking pictures and looking for potential organic materials at, or near the surface. We may one day soon land a spacecraft there to dig into the ice and look for signs of life. There’s quite an interest in drilling down through the ice to look for life directly in the ocean. Since the ice is very thick, that will be a huge undertaking. Though challenging, it could be a really important step in looking for life in an ocean of an icy moon like Europa.

You may have heard about our exploration of Mars. We’ve sent quite a few spacecraft to Mars. There have been flybys and orbiters, landers, and even rovers that drive around on the surface. Mars is a cold, rocky planet with a thin atmosphere, but it’s also one of the key places that we’re looking at right now as a place where life might have happened. Long ago, Mars had rivers and lakes and maybe even an ocean of water at the surface. It had a denser atmosphere than it does today and many active volcanoes. Ancient Mars had the chemical ingredients for life: there was energy (solar, geothermal, and possibly chemical), and plenty of water. When we send our orbiters, landers, and rovers to Mars, we’re keeping an eye out for potential signs of ancient life. For instance, the Curiosity rover, which is active on Mars right now, has cameras for looking at the structure of the rocks and minerals, it has instruments for looking at organic molecules in the Martian soil, and it also has an instrument for learning about the kinds of minerals that are present in samples of rock. Using these tools, Curiosity is looking for signs of past habitable environments on Mars. There may even be some potential places on Mars where things are living right now. Mars has lava tubes (caves formed by volcanoes), water ice in the ice caps identified by the Mars Reconnaissance Orbiter ( MRO ), and might have places in the subsurface where water is liquid and where life could be present. Orbiters, landers, and rovers will continue to reveal more information about Mars and whether it had, or maybe even has, life.

We’re only just beginning in our work to better explore our solar system and use our spacecraft and various instruments to look for possible signs of past or present life. With some skillful engineering and a little imagination, we’ll be able to design and build better tools for studying the solar system. We may even one day send humans out to search for signs of extraterrestrial life in the solar system. Our exploration has only just begun.

Portrait photo of Comic book scene of three rovers on red rocks. Leftmost rover burrows into rock with a metalic tool, center rover explores a large hole, and rightmost rover emits red laser light onto a rock in the foreground.
Rovers sent to Mars have payload instruments capable of analyzing the surface and shallow subsurface to search for signs of life. Payload instrumentscanuselaserspectroscopy and other analytical techniquestoget chemicalsignaturesofpossible biosignatures in rock and soil.
NASA/Aaron Gronstal

Grades 9-12 or Adult Sophisticated Learner

The scientific exploration of potentially habitable locations within our solar system is one of the most intriguing and exciting undertakings in human history. Even though we haven’t discovered life anywhere else yet, there are a lot of people who wonder if there was ever life, or might even be life right now, on other worlds right here around our own star. What do you think? If there is some form of alien life here in our solar system, how would we go about finding it? We humans can learn a lot by interacting with the world and using our own senses to make discoveries, but it turns out to be pretty hard to send humans to other worlds to explore. So far, the furthest humans have ever traveled away from our planet is just beyond the Moon. But, for us to send humans to worlds like Mars and the moons of the outer solar system it’s going to take some time. So, in the meantime, we send out robotic spacecraft as explorers for us. Sometimes we send spacecraft that will fly by another world and collect information, sometimes they go into orbit around the planet or other object in order to study it, and sometimes we even send robots that can land on the surface in order to look at these other worlds close-up!

When we design our spacecraft, we have to consider the kinds of tools that we want to send along in order to study things. The instruments that we put on the spacecraft will depend on the type of spacecraft it is, on the goals of the mission, and on where it’s going. Flyby and orbiter missions will often have cameras that are meant for getting pictures of worlds from afar and instruments that are good at characterizing atmospheres or measuring radiation around the world. Landers and rovers will gather data about the geology and history of the surface of another world. They might even look for signs of life by measuring organic molecules in surface samples. Future technologies for our exploration might include things like ice drills, submarines, underground robots, and spacecraft that can survive in the atmospheres of gas giants.

Mars is a good example of a place where we’ve been looking for signs of past or present life. Mars is a cold, rocky planet with a thin atmosphere, but, long ago, Mars had rivers and lakes and maybe even an ocean of water at the surface. It had a denser atmosphere than it does today and lots of active volcanoes. Ancient Mars had the chemical ingredients for life, there was energy, and plenty of water. When we send our orbiters, landers, and rovers to Mars, we keep an eye out for potential signs of ancient life. Our orbiters around Mars, like the Mars Reconnaissance Orbiter ( MRO ), can help in the search for life by taking really good pictures that give us a broad view of the environments on the surface and by using spectroscopy to measure the composition of surface environments. Spectroscopy is a fundamental technique in science where we measure how light interacts with matter to learn more about the chemical nature of that matter. Spectroscopy onboard our orbiters around Mars can allow us to measure the general types of minerals that are present over large regions of the Martian surface. Putting together information from these orbital pictures and spectroscopy allows us to pick the best places to send our landers and rovers. The Curiosity rover, which is active on Mars right now, has cameras for looking at the structure of the rocks and minerals up close, it has instruments for looking at organic molecules in the Martian soil, and it also has an instrument for learning about the kinds of minerals that are present in samples or rock. Using these tools, Curiosity is looking for signs of past habitable environments on Mars, like places where the minerals show signs of having formed in a watery environment. Although Curiosity isn’t necessarily looking directly for things that are alive now, there may be some potential places on Mars where things are living today. Mars has lava tubes (caves formed by volcanoes), water ice in the ice caps identified by the Mars Reconnaissance Orbiter ( MRO ), and might have places in the subsurface where water is liquid and where live could be present. Orbiters, landers, and rovers will continue to reveal more information about Mars and whether it had, or maybe even has, life.

Another place we’re exploring using spacecraft and specialized instruments is Europa, a moon of Jupiter. We now know that this world has an icy shell on top of a deep liquid water ocean. Our first images of Europa up-close came from the spacecraft Pioneer 10 and 11 and Voyager 2\. With Voyager 2, we saw for the first time that the icy crust of Europa has dark streaked lines all over it. These lines (which we refer to as “lineae”) were the first indication that the icy surface could be cracked and might have an ocean below. The Galileo spacecraft, which spent 8 years studying Jupiter and its moons (from 1995 to 2003), had an instrument onboard for measuring magnetism in the space environment. If you’ve ever put one magnet close to another, you’ve seen the effects of magnetism. We have tools that allow us to measure the effects of magnetism and they’re called “magnetometers”. Just as we can use a compass to tell us which way is north on Earth, a magnetometer can tell us about the magnetism coming from a planet or a moon. Our Earth produces a magnetic field due to the liquid metal outer core, which spins around and produces the field. Jupiter has the biggest and strongest magnetosphere in the solar system, and we’re pretty sure it’s formed by the movement of an ocean of liquid metallic hydrogen that acts as Jupiter’s outer core. The magnetometer instrument that was on the Galileo spacecraft showed us that Jupiter’s magnetic field is being disrupted around Europa due to a small magnetic field coming from Europa itself. This told scientists that there must be a salty liquid water ocean down below its surface.

On Earth, hydrothermal vents are a source of heat and energy on the ocean floor and have developed ecosystems around them where sunlight isn’t needed for energy. Could there be hydrothermal vent ecosystems within the ocean of Europa? With future spacecraft, we’ll flyby and even orbit Europa, taking pictures and looking for potential organic materials at or near the surface. The Europa Clipper mission will tell us more about Europa’s ocean, study the chemistry and geology of the surface ice, and will help us to figure out where we might want to send a lander. A lander mission to Europa will likely dig into the ice, just beneath the surface, to look at the chemistry and geology of the ice and to potentially look for organic molecules and isotopes that indicate the activity of life. There’s also a lot of interest in possibly drilling down through the ice to look for life directly in the ocean. That will be a big undertaking, since the ice is very thick, but could be a really important step in looking for life in an ocean of icy moon like Europa.

There are other icy moons in the solar system that we’re considering for possible signs of life. These include moons like Enceladus, Titan, Triton, and Ganymede. There have also been some proposals that there could be signs of life to be found in the clouds of Venus or maybe even within the icy material at the surface of a comet. We’re only just beginning in our work to better explore our solar system and use our spacecraft and various instruments to look for possible signs of past or present life. With some skillful engineering and a little imagination, we’ll be able to design and build better and better tools for studying the solar system and may even one day send humans out to search for signs of extraterrestrial life in the solar system. Our exploration has only just begun.

Portrait photo of Comic book scene of three rovers on red rocks. Leftmost rover burrows into rock with a metalic tool, center rover explores a large hole, and rightmost rover emits red laser light onto a rock in the foreground.
Rovers sent to Mars have payload instruments capable of analyzing the surface and shallow subsurface to search for signs of life. Payload instrumentscanuselaserspectroscopy and other analytical techniquestoget chemicalsignaturesofpossible biosignatures in rock and soil.
NASA/Aaron Gronstal