Kin beyond our ken?

Much international investment has taken place in space technology, including tentative efforts to locate extraterrestrial life, usually based on observations and interpretations of data.

Information from within our solar system has become available via manned missions, probes and other devices. Many of the Moon's and Mars' mysteries have been solved, and manmade probes have scrutinised a number of our solar system's planets.

Data on possible life from more distant solar systems are less accessible by direct technology, but are arguably implicit in scientific measurements, with a bit of intellectual deduction.

Using the Hubble Space Telescope, signals in the form of spectra (signal intensity plotted against the wavelength of radiation) originating from a planet (HD 189733b) orbiting a distant star (HD 189733) in our galaxy were measured. It is 63 light years from Earth in the direction of the constellation Vulpecula (the Little Fox). Some of us can remember where we were when this radiation started its journey circa 1944.

On 20 March 2008, scientists from the California Institute of Technology and University College London reported in Nature the rotational-vibrational spectrum of methane, CH4, in the region beyond the red end of the visible light spectrum in HD 189733b's atmosphere, stating "we can unambiguously determine that CH4 is present".

There has been growing evidence, too, of other extra-solar planets. At a meeting of the American Association for the Advancement of Science in Chicago in February, Alan Boss of the Carnegie Institute in Washington DC discussed estimates of many billions of them orbiting distant stars in our galaxy. Many could have life.

The formation of Earth is believed to have involved specific geophysical and astronomical factors, including the Moon's tidal effects on the oceans. These factors are linked to Charles Darwin's evolutionary theories. Are such conditions and outcomes unique?

The spectrum of methane in the infrared region shows a particularly impressive pattern of bands from rotational-vibrational changes. There is every reason to expect that spectra of equivalent or better quality could be measured at source on any cosmic body subject to suitable physical conditions and equipment. Methane is familiar on our own planet as the major component of natural gas. It is one of the simplest building blocks of life, and is associated with fossil deposits.

Evidence for distant life forms is difficult and expensive to pursue. Such evidence may better rest on intellectual considerations based on measurement.

To understand the spectrum of methane, scientists on Earth apply the mathematics not only of numbers (arithmetic), shape (geometry), symbols (algebra) and gradients and areas (calculus). They also apply the mathematics of properties that include symmetry, known as Group Theory, where numbers are replaced by elements of symmetry and arithmetical operations are replaced by symmetrical ones.

It can be shown that the geometrical structure of methane consists of a carbon atom connected to four hydrogen atoms placed at the four corners of a regular tetrahedron. This structure can easily be shown to possess various axes and planes of symmetry. If these five atoms formed any other shape, the spectrum would be different.

Does the existence of methane on an extra-solar planet suggest there is, has been or will be life on planets far from our solar system?

Scientific publications by this author were submitted to the 2001 and 2008 research assessment exercises, including papers contributing to the molecular mechanism of neurotransmission for Alzheimer's disease. If methane exists in alien worlds, will there also be neurotransmitters for which the same scientific properties apply?

Will this also be the case for the "humanities"? For example, theology: will there be alien religions paralleling ours? And will there be alien sociologists writing columns in the equivalent of Times Higher Education? We may never know, but it is reasonable to believe that if methane exists in their world, aliens will use the same science to understand its properties as we practise here, or to borrow a well-known theological expression, "on Earth as it is in heaven".