Mixed results in search for life on other planets

Astronomers have in recent times recorded mixed results in their search for signs of life on other planets. While a group of astronomers have found at least 45 planets orbiting distant stars that possess Earth-like qualities including a similar atmosphere and life sustaining liquid, water, as well as spotting possible marker of life, phosphine gas, on Venus; another team found no technological signs of alien life in study of more than 10 million star systems. This is as another research established difficulty in finding evidence of life on Mars.

Also, a new United Nations (UN) report has warned that while global warming has led to rising tides, it is also threatening the water supply of 3.2 billion people around the world. According to the report, the number of people living in places with insufficient water will shoot up almost 60 percent in the next 30 years.

In another study, it was established that global warming could trigger spread of fatal mosquito-borne diseases such as dengue fever to other continents.

According to researchers at Cornell University and at Spain’s Centro de Astrobiología, while scientists are eager to study Mars’ (the red planet’s) soils for signs of life, researchers must ponder a considerable new challenge: Acidic fluids – which once flowed on the Martian surface – may have destroyed biological evidence hidden within Mars’ iron-rich clays.

The researchers conducted simulations involving clay and amino acids to draw conclusions regarding the likely degradation of biological material on Mars. Their paper, “Constraining the Preservation of Organic Compounds in Mars Analog Nontronites After Exposure to Acid and Alkaline Fluids,” was published September 15 in Nature Scientific Reports.

In the search for life on Mars, the red planet’s clay surface soils are a preferred collection target since the clay protects the molecular organic material inside. However, the past presence of acid on the surface may have compromised the clay’s ability to protect evidence of previous life.

“We know that acidic fluids have flowed on the surface of Mars in the past, altering the clays and its capacity to protect organics,” the researchers said.

They said the internal structure of clay is organized into layers, where the evidence of biological life – such as lipids, nucleic acids, peptides and other biopolymers – can become trapped and well preserved.

After a long exposure to Mars-like ultraviolet radiation, the experiments showed photodegradation of the glycine molecules embedded in the clay. Exposure to acidic fluids erases the interlayer space, turning it into a gel-like silica.

“When clays are exposed to acidic fluids, the layers collapse and the organic matter can’t be preserved. They are destroyed. Our results in this paper explain why searching for organic compounds on Mars is so sorely difficult,” the researchers said.

Meanwhile, according to another study, published Monday in the journal Nature Astronomy, life may exist on Venus after scientists discovered phosphine gas hidden in the planet’s clouds.

The gas has been detected in the atmosphere of Venus, which indicates it could host unknown photochemical or geochemical processes.
On Earth, phosphine – a colourless gas that has the smell of garlic or decaying fish – is produced predominantly by anaerobic biological sources – organisms, which don’t require oxygen to grow.

And small amounts of the gas occur naturally from the breakdown of organic matter. While the conditions on the surface of Venus – the second planet from the Sun – are hostile to life, the environment of its upper cloud deck, around 53-62km (33-38 miles) above the surface, is temperate.

Jane Greaves, from Cardiff University, and colleagues observed Venus with the James Clerk Maxwell Telescope and the Atacama Large Millimeter/submillimeter Array in 2017 and 2019, respectively.

They detected a spectral signature – a code which material emits with respect to wavelengths – that is unique to phosphine, and estimated an abundance of 20 parts-per-billion of phosphine in Venus’s clouds.

Researchers looked at different ways the gas may have been produced, including from sources on the surface of the planet, micrometeorites, lightning, or chemical processes happening within the clouds.

But they were unable to determine the source of the phosphine. However, they argue that the detection of the gas is not robust evidence for microbial life and only indicates potentially unknown geological or chemical processes occurring on the planet.

And, according to the study, published in Nature Astronomy, the make-up of the planet’s clouds is highly acidic, meaning in such conditions phosphine would normally be destroyed very quickly.

The researchers said further observations and modelling are needed to explore the origin of the gas in the planet’s atmosphere. Meanwhile, in the first study, published in the journal Proceedings of the Royal Society A, experts from Luleå University of Technology, Sweden, have created a new way to determine the habitability of these distant worlds by studying their atmosphere.

The team found a way to use information on “atmospheric species”, that is chemicals in the atmosphere, and how fast they escape into space to determine how close an exoplanet is in terms of temperature and composition to the Earth.

They then used their new model on the 55 potentially habitable worlds listed in the existing exoplanet catalogue – which focuses on habitable zone and the host star.

Only 17 of the 55 planets in the catalogue met the criteria defined by the Swedish researchers for being “Earth-like” but the team found another 28 planets on the wider exoplanet list that also met the criteria – bringing the total of Earth-like worlds to 45.

Advanced ground and space based missions including the current CHEOPS and future James Webb telescope can now use this research to focus their searches.

The team explained detecting habitable exoplanets is a difficult challenge, as we can’t just ‘send a probe’ the vast distances between stars.

The nearest exoplanet with a potentially habitable atmosphere is Proxima b around the star Proxima Centauri 4.22 light-years – or 25 trillion miles away.

Currently, determining an exoplanet’s capability to host life relies on the restricted low-resolution spatial and spectral information of their atmospheres.

To create a “short list” of habitable worlds, the team used the ‘kinetic theory of gases’ – how the gases move about the atmosphere – and a list of possible chemical retained in the atmospheres of currently known exoplanets.

Meanwhile, Australian astronomers reported they have found no technological signs of alien life in a study of more than 10 million star systems.

According to the study published in Publications of the Astronomical Society of Australia, Perth-based researchers used the Murchison Widefield Array (MWA) radio telescope in the Western Australian outback, in a project dubbed “looking for ET”.

The MWA searches for powerful radio emissions at low frequencies, similar to FM radio frequencies on Earth that allow radio broadcasts. These emissions from space, known as “technosignatures”, could possibly indicate the presence of intelligent aliens with technological innovations similar to our own.

The team completed the “deepest and broadest search” of a patch of sky known to include at least 10 million stars, in the southern constellation of Vela.

But the researchers concluded that, in this part of the universe, other civilisations are “elusive, if they exist” at all.
Meanwhile, a new study showed climate change could trigger the spread of potentially fatal mosquito-borne diseases around Africa and beyond.

According to the study published in Lancet Planetary Health, disease-carrying mosquito species, such as the Aedes aegypti or yellow fever mosquito, are attracted to the excess heat caused by climate change.

United States (U.S.) researchers have predicted when and where in Sub-Saharan Africa malaria will decrease and other mosquito-borne diseases will rise.

They also warned of “public health disaster” if the continent fails to focus on strategies tailored to mosquito-borne diseases other than malaria.

They highlighted that different species of the flying pest thrive at various temperature ranges and transmit different diseases. The anopheles gambiae mosquito transmits malaria to humans, but Aedes aegypti is also a huge threat and transmits several different viruses, including the dengue virus.

“Climate change is going to rearrange the landscape of infectious disease,” said Stanford biologist and study lead author Erin Mordecai. “Chikungunya and dengue outbreaks like we’ve recently seen in East Africa are only becoming more likely across much of the continent. We need to be ready for this emerging threat.”

The nighttime-biting Anopheles gambiae mosquito transmits malaria, a disease that affects more than 200 million people in Sub-Saharan Africa, and killed more than 400,000 people there in 2018.

Public health efforts in the region have already tried to tackle malaria with insecticide-treated bed nets and indoor spraying, among other measures.

But these control strategies do little to combat the daytime-biting Aedes aegypti mosquito, commonly known as the yellow fever mosquito.
Aedes aegypti can transmit a range of devastating diseases, such as Rift Valley Fever, Zika, chikungunya and dengue, as well as yellow fever.

Growing urbanisation has expanded Aedes aegypti’s range by enlarging its preferred breeding grounds, including human-made containers such as discarded tires, cans, buckets and water storage jugs.

In contrast, malaria-transmitting mosquitoes breed in naturally occurring pools of water more common in rural areas. Expanding urban areas also form ‘heat islands’ that are several degrees warmer than surrounding vegetated areas, which is attractive to the warm weather-loving Aedes aegypti.

Past research has found that warmer temperatures increase transmission of vector-borne disease up to an optimum temperature or “turn-over point”.