If water comes, can life be far behind?

NASA’s Mars Reconnaissance Orbiter (MRO) recently detected intermittent signs of liquid water in present day Mars. This finding provides the strongest evidence yet for the presence of liquid water in the red planet after fifteen years of intensive exploration. While researchers believe Mars was once a warm and wet planet which could have supported life, it is believed that its smaller size, lesser gravity and thinner atmosphere as compared to earth could have led to most of the water being evaporated and lost into space.

Mars now is an extremely cold planet which implies that the liquid water is likely to be highly salty, as pure water freezes at 0°C and salt impurities lower the freezing point. It is also likely that the kind of salt present is not the typical Sodium chloride, but more toxic ones such as perchlorate.

What is exciting about Mars having liquid water?

Scientists are excited as the presence of liquid water is integral for life to originate, at least on Earth. Though life may originate without water elsewhere, we are not aware of such an event and therefore the interest for finding life outside Earth with or without water is still high.

While the highly salty water in Mars sounds unpalatable for us and most other animal and plant species, there are some organisms capable of thriving in such extreme environments. Halophiles are such organisms (usually bacteria or archaea) that are found in high salt containing environments in Earth like the Red sea, the Great Salt Lake and the briniest of marshes and even Antarctica. “I think it’s quite possible there are halophiles that could survive on Mars”, says halophile researcher Shiladitya DasSarma from the University of Maryland.

Why should we be interested in microbes that thrive in extreme environments that are toxic to us?

Organisms such as halophiles with adaptations for extreme environments are highly useful for industrial and research purposes. It’s because they produce proteins that possess unusually high resilience to heat, salt or chemical exposures and other drastic environments. For example, the halophiles’ ability to survive in high salt solutions also makes them useful for processes where there’s little or no water, such as catalysing chemical reactions in organic solvents.

Researchers borrowed an enzyme from a bacteria that thrives in the hot springs in Yellowstone National Park at temperatures as high as 131 °F to invent one of biology’s most useful tools—polymerase chain reaction, or PCR. PCR is now used in DNA cloning for sequencing, diagnosis of hereditary diseases, genetic fingerprinting in forensics and paternity testing, and detection and diagnosis of infectious diseases.

The University of Connecticut chemist Robert Birge is working with proteins from the halophileHalobacterium salinarum, an archaea found in salt marshes. The organism makes a protein called bacteriorhodopsin, a pigment that dyes marshes a deep red or purple. Since the pigment is used by the organism to absorb light and use it for energy, he’s been adapting it for optical memory storage and optical processing. A few years ago, one of his students conceived of using bacteriorhodopsin for an artificial retina. Now they’ve built prototypes and found they can restore sight in animals.

When can we see the evidence for life on Mars, if it exists?

There is an intense debate going on about how to collect material from wet places on other planets without contaminating them with earth-borne life. An organisation called the Committee on Space Research (Cospar, of the International Council for Science) draws up the rules on what is called planetary protection, which exist to prevent missions from Earth contaminating the pristine environments of other worlds. Landers that are searching for life must be exceptionally clean, but those entering special regions must be cleaner still. It will be interesting to see how such challenges are overcome in our quest for finding life elsewhere.

BY SIDDHARTH JANARTHANAN ON DECEMBER 15, 2015.

NEWS FROM:BIOTECHIN.ASIA

Impurities 雜質

Sodium chloride 氯化鈉

Perchlorate 高氯酸鹽

Halophiles 嗜鹽菌，需要最少0.2M鹽濃度生活的生物。

Microbes 微生物，嗜極生物（英文：Extremophile），或者稱作嗜極端菌，是可以（或者需要）在「極端」環境中生長繁殖的生物，通常爲單細胞生物。

Resilience 彈性

Drastic 激烈

Catalyzing 催化

Enzyme酶

polymerase chain reaction聚合酶鏈反應

hereditary diseases 遺傳性疾病

Antarctica 南極洲

NASA’s Mars Reconnaissance Orbiter美國宇航局的火星勘測軌道飛行器