Scientists look to moons in search of elusive life
Scientists from space agencies around the world have for many years been searching for extraterrestrial life forms in the universe. But despite the endless possibilities, physical constraints make it an extremely difficult endeavour.
Scientists involved with the Search for Extraterrestrial Intelligence (SETI) project have set up giant radio telescopes in the hope of receiving signals from the closest civilisations.
“They might be at least a few hundred light years away,” said Ng Tze-chuen, a planetary sampling expert who has been involved in numerous exobiology missions. “I doubt very much if aliens are as technologically advanced as humans who can use transmitters to send and receive signals across space.”
Ng said they were not likely to be advanced because the Earth was “in a perfect alignment position in our solar system from the sun”, which is a rare phenomenon in the universe.
“We have giant Jupiter which helps to absorb all the meteorite punches that could wipe out our civilisation,” he said. “There are billions of stars in our universe. But only Earth-like planets with the right atmosphere, temperature and chemistry could be the ingredients for life.”
He said given the huge distance between us and stars, it remained impossible for humans to travel beyond the solar system to meet other civilisations. “Even aliens with a long lifespan from the most advanced civilisation could not survive such travel.”
He said because distant life forms were hard to discover, many exobiology missions focussed on finding evidence of extinct life on nearby planets or moons.
“When we went on Mars missions, we were all hoping to find evidence of extinct life forms.”
Ng said he was more excited about missions to Europa, one of the moons orbiting Jupiter, than those to Mars. He added that the recent discovery of a warm underground ocean with geysers ejecting plumes on Europa had completely shifted the target from Mars to the moons of giant planets such as Jupiter and Saturn.
“Mars only has ice but Europa has liquid water. Europa potentially has a warm ocean under its icy shell,” he said.
He said if humans did discover traces of life on Mars, it could still have come from Earth.
“Primitive life forms such as seeds could be carried to Mars on the debris of meteorites that hit the Earth before,” he said, “But if we discovered life on Europa, it would prove that the universe is full of life.”
According to the Lunar and Planetary Institute, the following are the five essential conditions for life to exist on a planet.
Temperature essentially influences how quickly atoms and molecules move. For life to thrive a planet would need a stable temperature range from minus 15 degrees to about 115 degrees Celsius. In this range, liquid water can still exist under certain conditions.
Water is critical in dissolving and transporting chemicals within and to and from a cell. Water is a vital ingredient in photosynthesis, the process which converts sunlight into sugars and thus provides the energy source for most life.
An atmosphere is crucial in generating greenhouse effects and shielding the surface of a planet from excessive radiation. In order for plants to carry out photosynthesis, there must be a sufficient amount of carbon in the atmosphere in the form of carbon dioxide.
Organisms require light or chemical energy to run their life processes. Only with a steady input of either light or chemical energy can cells run the chemical reactions necessary for life.
Nutrients are used to build and maintain the body of living organisms. Earth has a water cycle, an atmosphere and volcanoes to circulate nutrients. Planets without systems to deliver nutrients to its organisms cannot support life.
Additional reporting by Josh Ye