The story of two alleged "alien" corpses, which aroused sensation after being presented to the Mexican Congress by Mexican journalist and UFO enthusiast Jose Jaime Maussan on September 12, has seen new developments.

Contrary to suggestions that the bodies were fabricated using animal or human bones, scientists at a lab in Mexico City claimed tests showed that the mummified bodies had not been assembled or manipulated, The Telegraph reported on September 19.

"[They] belong to a single skeleton that has not been joined to other pieces," Jose de Jesus Zalce Benitez, director of the Health Sciences Research Institute of the Secretary of the Mexican Navy, who carried out the tests, was quoted as saying.

However, given the relationship between Benitez and Maussan, who "appeared alongside each other at the Mexican Congress to give evidence of their discoveries," the test result "is unlikely to assuage Maussan's critics," said The Telegraph.

No aliens in solar system

The scientific community has been skeptical about the discovery.

NASA Administrator Bill Nelson called for shifting the conversation "from sensationalism to science."

Yang Yuguang, vice chair of the Space Transportation Committee at the International Astronautical Federation, told CGTN that so far no high-level life forms have been found in the solar system beyond Earth, based on scientific exploration missions.

"There do not exist any intelligent life forms, or aliens, in other celestial bodies of the solar system" at least until now, as people have launched probes to study almost all major celestial bodies, including Mercury, Venus, Mars, Jupiter, Saturn, Uranus, Neptune and even Pluto, in the solar system, said Yang.

"But we cannot deny the possibility that during the past or at the current stage, there are some simple life forms such as germs, bacteria or virus," said Yang.

If there were, how could they be detected?

Yang noted that detecting the evidence of life forms either inside or outside the solar system, or the search for extraterrestrial intelligence (SETI), is one of the major tasks in space exploration.

Taking the Mars probe as an example, Yang said its scientific payloads, such as the camera and the laser, enable the analysis of the components on the Martian surface, which can provide traces of water or fluid in the ancient age and shed light on possible life forms at that time.

However, limited by current knowledge and technologies, the expert said the study of other star systems can now only resort to "indirect measures," such as optical and radio telescopes.

China's 500-meter Aperture Spherical Radio Telescope (FAST), also known as the "China Sky Eye," is one of the scientific approaches for SETI, Zhang Tongjie, professor in astronomy at Beijing Normal University, told CGTN.

Zhang said there were three main methods for SETI detection, namely radio SETI, optical SETI and astrobiology research.

"The radio SETI involves scanning the radio spectrum for narrow band signals that could be the indicative of artificial communication between ETs and our Earth," said Zhang, adding that some institutes are doing such research by examining a wide range of frequencies and analyzing the collected data.

"But so far, they did not find any ET signals," said Zhang.

He said SETI in China is a relatively new field, with the first SETI observation at FAST starting four years ago.

In August, FAST helped Chinese scientists detect distinct "dwarf pulses" from a bright pulsar coded as PSR B2111+46.

The idea of optical SETI, Zhang explained, is to detect potential laser or light signals from extraterrestrial civilizations.

Astrobiology research, with instrument like the James Webb Space Telescope and some ground-based observations, aims to understand the conditions and requirements for life to exist elsewhere in the universe, said Zhang.

"These surveys provide valuable data for understanding the distribution of planets in our galaxy, helping we SETI researchers target our search for potentially habitable worlds," he said.