Carl Sagan detected life on Earth 30 years ago — here’s how his experiment is helping us search for alien species today

Subject :Science and Tech

Section: Health

Context:

In 1993 a group of scientists led by Carl Sagan found evidence for life on Earth using data from instruments on board the Nasa Galileo robotic spacecraft.

Galileo spacecraft:

NASA’s Viking spacecraft, launched in the 1970s, was aimed to detect life on Mars.
Galileo launched in October 1989 on a six-year flight to Jupiter.
It has a variety of instruments designed to study the atmosphere and space environment of Jupiter and its moons. These included imaging cameras, spectrometers (which break down light by wavelength) and a radio experiment.
Outcome of Galileo:
- The near infra-red mapping spectrometer (NIMS) instrument detected gaseous water distributed throughout the terrestrial atmosphere, ice at the poles and large expanses of liquid water “of oceanic dimensions”.
- It also recorded temperatures ranging from -30°C to +18°C.
Galileo’s plasma wave radio experiment:
- The emission from a given natural source occurs across many frequencies. Artificial radio sources, by contrast, are produced in a narrow band.

Signals for detecting life elsewhere:

A strong case for life elsewhere will likely require a combination of mutually supporting evidence, such as light absorption by photosynthesis-like processes, narrowband radio emission, modest temperatures and weather and chemical traces in the atmosphere which are hard to explain by non-biological means.

Source: DownToEarth