As far as we know, life exists only on Earth. We don’t have any solid evidence to say that there is any extraterrestrial life. But as intelligent living beings, we always have the quest to find extraterrestrial life and we have been trying to do that.
The first place we can look at for some life is obviously our own Solar system. So, in this blog let us see about the places where extraterrestrial life might exist and let us also see about some missions which we sent into space in the search for life.
Index
The Habitable Zone
To search for life in our solar system, we need to start at home. Because Earth is our only example of a planet endowed with life, we can use it to understand the conditions needed to spawn life elsewhere. As we define these conditions, though, we need to consider whether they are specific to life on Earth or general enough to apply anywhere.
Many astrobiologists believe that in order for life to arise and survive, we must find it on a planet or moon within the habitable zone or the Goldilocks zone of a star. The habitable zone refers to the region around the star in which
- Liquid water can form and remain liquid.
- The size of the star is important. Stars that are much larger than the Sun have short lifetimes, that it is unlikely that there would be enough time for any kind of life to develop.
- There is a special zone around the star where the temperatures are right and life like us can exist there only.
Another key ingredient to the formation of life seems to have a large planet – like Jupiter – in a planetary system. Because Jupiter is so much more massive than all the other planets, it attracts many asteroids, comets, and other objects that travel within the Solar System. This is important because otherwise, some of these objects would end up crashing into Earth, and many did in the very early formation of the Solar system.
Where in the Solar System?
The locations in our solar systems which at least have a few of the above things and are thus considered most likely to harbor life are:
- Mars
- Europa and Ganymede, two of the Galilean moons of Jupiter
- Titan, a moon of Saturn
The reason these locations are considered more likely than, say, Mercury or our Moon, is because there is evidence that each of these worlds either had some liquid on its surface in the past or has subsurface liquid (water in the case of Mars, Europa, and Ganymede, and liquid hydrocarbons in case of Titan) or on the surface now. This property is considered by many scientists as the single most important requirement for life to exist.
Why not Mercury and Venus?
Mercury is not considered to be a planet with life. It is too close to the Sun, extremely hot and dry, and has a very little atmosphere. Venus is equally inhospitable, which is surprising given that it would seem to have a lot in common with Earth. They are similar in size and masse and Venus is only 28% closer to the Sun than Earth.
The carbon dioxide atmosphere on Venus acts as a greenhouse gas and as a result, the surface of Venus has an average temperature of 460°C. Scientists believe that Venus had water at one time in the past, but conditions in the atmosphere caused the planet to become too hot and all the water has evaporated into space.
Mars
Scientists have been curious for centuries about whether there is life on Mars. Mars, This is the word most associated with alien life, and will be the first to be populated by human beings, should we survive long enough, and have the willingness to migrate beyond our planetary home.
The Red Planet was once awash with water, but climatic changes billions of years ago stripped that world of liquid water and most of its atmosphere. We may find fossilized remains of ancient life there, and there is a possibility some form of life still exists within the ice hidden under its ruddy surface.
Mars have a pretty extreme climate with daytime temperatures reaching 20-degree Celsius at the equator which can go as low as -153 degree Celsius at poles. Ar equator, there are pretty favorable temperatures according to various mission data and this is where the hope for our habitation lies.
Mars is the most explored planet in our solar system, other than the Earth. We have sent various missions to the planet including rovers, satellites etc.
The next possible place is on the moons of Jupiter and Saturn
Moons of Jupiter And Saturn
Combined, the gas giants Jupiter and Saturn have almost 150 confirmed moons, ranging from asteroidal, rocky objects to planet-sized, geologically complex worlds. Hidden amongst the immense variety of lunar shapes, features, and environments, now let us see a few places where life could be possible:
Europa
Europa, the smallest of the four Galilean moons of Jupiter is roughly 90 percent the size of our own Moon and is home to some of the largest oceans in the Solar System. Although most of this water lies under the surface, heating caused by the tidal forces of Jupiter and other large moons keeps large portions of these oceans liquid, increasing the chances of life developing there. The first hints of these oceans were provided in 1979, during visits by the Voyager spacecraft.
Ganymede
Ganymede, which is the largest moon in the solar system, also seems to have a saltwater ocean beneath an ice crust. The energy from the tidal interactions between Ganymede and the other Galilean moons should not generate enough energy to keep saltwater liquid on this moon, and astronomers think the water is kept liquid by a liquid iron core inside the moon, and the insulation of the ice which is hundreds of kilometers thick. Ganymede also seems to have a very thin atmosphere.
Titan
In contrast, Saturn’s largest moon, Titan, stands out from all other moons in the Solar System, as it not only is the only moon to have a dense atmosphere, but it is also the only place in the Solar System – other than Earth – where stable bodies of liquid can be found on the surface. In many ways, Titan challenges conventional wisdom about the characteristics and composition of moons. Larger than the planet Mercury, Titan has more in common with Earth than other moons; it has a seasonal climate, weather, and familiar surface features like rivers, dunes, and deltas. However, Titan’s atmosphere is nitrogen, not oxygen, and the interesting seas and rivers on its surface are liquid methane and ethane, not water.
Enceladus
Enceladus, the sixth-largest moon of Saturn, has some amazing features that make it very interesting to astrobiologists. It is white and reflects almost 100% of the light that strikes it. It also has geysers on its surface that shoot out jets of water with ammonia and organic compounds. The temperatures near these geysers are likely very high, while the rest of the moon is freezing with an average temperature of about -220°C.
Now, let us look at some of the famous missions sent to these places in search of life.
Missions
There have been many space missions for finding life out there in the Solar System.
Here is the full list for you
1. List of missions to the outer planets.
2. List of missions to Mars
So, as you can see that there were a lot of missions on mars and outer planets, let us see only a few and most important missions.
Curiosity Rover
Curiosity is a car-sized rover made to explore the Gale Crater on Mars as part of NASA’s Mars Science Laboratory mission. Curiosity was launched on November 26, 2011, from Cape Canaveral, and landed on Mars on August 6, 2012. The rover’s goals include an investigation of the Martian climate and geology, assessment of whether the selected field site inside Gale has ever offered environmental conditions favorable for microbial life, including investigation of the role of water, and planetary habitability studies in preparation for human exploration.
Curiosity has sent us a lot of valuable images of Mars.
Curiosity is still operational and has helped us learn about a lot of things related to mars. The next rover to Mars is the Perseverance rover which is designed much like Curiosity only and it will be carrying different scientific instruments to Mars for further exploration.
Cassini–Huygens
The Cassini–Huygens space-research mission was a collaboration between NASA, ESA, and the Italian Space Agency (ASI) to send a probe to study the planet Saturn and its system, including its rings and natural satellites. The robotic spacecraft comprised both NASA’s Cassini probe and ESA’s Huygens lander, which landed on Saturn’s largest moon, Titan.
The data recorded Huygens was first sent to Cassini and then Cassini sent it to Earth. Huygens successfully gave us 350 images of Titan but another 350 couldn’t be received due to some issue in Cassini.
NASA has planned to send a rotorcraft called Dragonfly to Titan in 2034 for further study of this Moon.
There were a total of nine spacecrafts that were launched on missions that involve visits to the outer planets. All nine encountered Jupiter and some of its moons. There haven’t been missions especially to Ganymede and Europa but there are planned missions like Jupyter Ganymede Orbiter and Europa Clipper.
Let us now wait and see whether we find any life be it in any form on any of these places in our Solar System. Even a trace of any micro-organism of another planet would be of very high value for us in terms of understanding life.
