To date, no proof of past or present life has been found on Mars. Cumulative evidence suggests that during the ancient Noachian time period, the surface environment of Mars had liquid water and may have been habitable for microorganisms, but habitable conditions do not necessarily indicate life.
But on Mars, carbon dioxide is 96% of the air! Meanwhile, Mars has almost no oxygen; it's only one-tenth of one percent of the air, not nearly enough for humans to survive. If you tried to breathe on the surface of Mars without a spacesuit supplying your oxygen – bad idea – you would die in an instant.
It has been speculated that life on Venus may have come to Earth through lithopanspermia, via the ejection of icy bolides that facilitated the preservation of multicellular life on long interplanetary voyages. "Current models indicate that Venus may have been habitable.
Among the stunning variety of worlds in our solar system, only Earth is known to host life.
Meanwhile, Mars has almost no oxygen; it's only one-tenth of one percent of the air, not nearly enough for humans to survive. If you tried to breathe on the surface of Mars without a spacesuit supplying your oxygen – bad idea – you would die in an instant.
Jupiter's environment is probably not conducive to life as we know it. The temperatures, pressures, and materials that characterize this planet are most likely too extreme and volatile for organisms to adapt to.
Mercury's environment is not conducive to life as we know it. The temperatures and solar radiation that characterize this planet are most likely too extreme for organisms to adapt to.
Jupiter cannot support life as we know it. But some of Jupiter's moons have oceans beneath their crusts that might support life.
The fourth planet from the sun, Mars has geological features like the Earth and moon, such as craters and valleys, many of which were formed through rainfall. Although there is a growing body of evidence that there was once water on Mars, it does not rain there today.
So far, only uncrewed spacecraft have made the trip to the red planet, but that could soon change. NASA is hoping to land the first humans on Mars by the 2030s—and several new missions are launching before then to push exploration forward.
Problem 3 – Which planet has the atmosphere with the greatest percentage of Oxygen? Answer: From the table we see that Mercury has the greatest percentage of oxygen in its atmosphere.
It's about 3.6 billion miles away from the Sun, and it has a thin atmosphere composed mostly of nitrogen, methane, and carbon monoxide. On average, Pluto's temperature is -387°F (-232°C), making it too cold to sustain life.
Gas giants are unlikely to host life as we know it, as they are huge balls of gas with no substantial surface. That said, there is a possibility of finding microbial life at their various icy moons, or perhaps there are other possibilities of life that science has not yet considered.
Potential for Life
The temperatures, pressures, and materials that characterize this planet are most likely too extreme and volatile for organisms to adapt to. While planet Saturn is an unlikely place for living things to take hold, the same is not true of some of its many moons.
Uranus' environment is not conducive to life as we know it. The temperatures, pressures, and materials that characterize this planet are most likely too extreme and volatile for organisms to adapt to.
Uranus holds the record for the coldest temperature ever measured in the Solar System: a very chilly -224℃. The temperature on Neptune is still very cold, of course – usually around -214℃ – but Uranus beats that. The reason why Uranus is so cold is nothing to do with its distance from the Sun.
Most astronomers feel that it would be impossible for life to exist on Venus. Today, Venus is a very hostile place. It is a very dry planet with no evidence of water, its surface temperature is hot enough to melt lead, and its atmosphere is so thick that the air pressure on its surface is over 90 times that on Earth.
Additionally, Titan's rivers, lakes and seas of liquid methane and ethane might serve as a habitable environment on the moon's surface, though any life there would likely be very different from Earth's life.
Europa's surface is blasted by radiation from Jupiter. That's a bad thing for life on the surface – it couldn't survive.
The Cassini mission launched in 1997 and spent seven years traveling to Saturn, arriving in 2004. Cassini is the first spacecraft to orbit Saturn, and has provided a treasure trove of data and images of the entire Saturnian system.
Crewed missions
Actually, the probe secretly carried two North Korean cosmonauts, Lee Jung-Gil and Park Chol. While the latter was killed during the landing, Lee became the real first man setting foot on Mars on February 8, 1995.
Water, water everywhere—and not a drop to drink. In 1972, scientists were astonished to see pictures from NASA's Mariner 9 mission as it circled Mars from orbit. The photos revealed a landscape full of riverbeds—evidence that the planet once had plenty of liquid water, even though it's dry as a bone today.
He can quote the easy answer for why we go to Mars, the assumption most scientists and science writers make: Mars is close. It's practically right next door, and you can fling a robot there in half a year. “That's the NASA answer. It's the most accessible place for life other than on Earth.
The International Astronomical Union (IAU) downgraded the status of Pluto to that of a dwarf planet because it did not meet the three criteria the IAU uses to define a full-sized planet. Essentially Pluto meets all the criteria except one—it “has not cleared its neighboring region of other objects.”