Login with your Social Account

Representation of dna body strand

Researchers find evidence of DNA and RNA even before life on Earth

Scientists have found a piece of strong evidence that both DNA and RNA might have been formed from the same precursor molecules even before the evolution of life on Earth. The research published in Nature Chemistry shows that the first living beings on our planet might have had both RNA and DNA like all other cellular-based life forms. This is in contrast to the current understanding that the earliest life forms only possessed RNA and DNA was formed with the evolution of life. This is commonly known as the RNA World Hypothesis. After this new finding, scientists should not fully rely on the RNA World Hypothesis for carrying out investigations on the origin of life on Earth.

RNA and DNA are chemically quite similar but chemists have not been able to show how one could have been converted to the other in earliest stages of our planet without the help of enzymes which are produced by the organisms. Because of this reason, researchers have always concluded that RNA is the basic component of the earliest life forms. RNA can store genetic information like DNA and also store catalyse biochemical reactions like protein enzymes. Hence it could have performed the basic biological functions in the earliest forms of life.

Ramanarayanan Krishnamurthy, a chemistry professor at Scripps Research along with his colleagues found a compound which was present in pre-biotic Earth and performed the essential task of linking RNA blocks to larger RNA strands and could have done the same for proteins and DNA.

Scientists have identified a compound named thiouridine which was likely to be present on Earth before the formation of life and it could have been a chemical precursor to the nucleoside blocks of the early RNA. It was found that by means of few chemical reactions this compound could be transformed to deoxyadenosine, a basic building block of DNA. They could also convert thiouridine to deoxyribose which is very closely related to deoxyadenosine.

These findings are a strong indicator that both RNA and DNA developed together and were present in the earliest life forms. Scientists have also suggested that both RNA and DNA might have been combined to form the first genes.  Although no such organism has occurred naturally but a  paper by Scripps Research described an engineered bacteria which can survive with genes formed by a combination of RNA and DNA.

Irrespective of the ways in which life formed, both RNA and DNA with their respective strengths and weaknesses would have arranged themselves into a proper division of labour as evident in the cells today.

Curiosity on Surface of Mars

Scientists report release of methane on the surface of Mars

In 2013, NASA’s Curiosity reported about the detection of methane on Mars. This was a significant finding, as methane was detected at various sites on Mars but it simply disappeared after a time. There has been always a debate on the amount and the nature of methane present in Mars. Now, the presence of methane has been confirmed by the Mars Express.

This is an interesting finding as terrestrial methane can be made either by living organisms as well as by geological processes. As methane has a short lifespan in the atmosphere of Mars, so detection of the gas means that it has been released recently. The finding has been confirmed by Planetary Fourier Spectrometer( PFS)  which is present on Mars Express.

Marco Giuranna, PFS’ principal investigator reported that they detected about 15 parts per billion by volume of methane in the Martian atmosphere. Parts per billion is a small amount but this is a remarkable finding for Mars. It is estimated that 46 tonnes of methane was present in 49,000 square kilometres on an average.

After the detection by Curiosity, it was thought that the source of methane might have been the north of the Curiosity rover and it was released from the Gale Crater which is the landing location of Curiosity.

But the question remains on the origin of methane. There are multiple opinions on this. One way is by micro-organisms. If the methane is produced by them a long time ago and it is trapped in ice, then the melting of ice can release it in the atmosphere.

Methane can also be produced by geological processes which do not require living beings at all. It can be produced as a by-product of serpentinisation, in which mineral alteration occurs in the crust with help of heat and water.

Researchers searched the region of Gale crater for features from which gas seepage can be expected. In Earth, this process is very well known to occur along tectonic faults and gas fields. Giuseppe Etiope, from the National Institute of Geophysics and Volcanology in Rome, reported that tectonic faults were identified which may extend far below the region expected to contain ice. Permafrost is a brilliant source in which methane gets trapped. It is very much possible that the methane is released along with the faults which pass through the ice. Hence this investigation shows that we may be familiar with the surface of Mars but we do not have much knowledge on its interior.