Interview Astrophysicist Sara Seager: "It will be very difficult to find an Earth twin planet"
NASA will send two missions Europa also returns to Venus: it will send a spacecraft to X-ray the planet
When the Earth is the exoplanet From which extraterrestrial worlds could they find us?
With three missions on the agenda to be dispatched in the next 10 years, Venus has regained prominence in space exploration. One of the main enigmas about this planet that once resembled ours is to clarify whether there is life in its clouds despite its high sulfuric acid content, as suggested by the announcement last September that phosphine, a gas, had been found. that on Earth produce living beings.
Several studies have questioned this work and this Monday, another investigation that has measured the water in its clouds maintains that the amount is so low that not even terrestrial organisms capable of withstanding the most extreme conditions could survive in the Venusian atmosphere. The new study, published in the journal
Nature Astronomy,
represents a jug of cold water for the phosphine theory, since in practice it
concludes that its clouds would not be habitable.
"We have not discovered that the water level is slightly below what the most extreme organisms need, but that it
is a hundred times lower than it would be necessary"
, explained in a virtual press conference John E. Hallsworth, leader of this international study with Spanish participation that has measured and compared the amount of water in the atmospheres of Venus, Mars and Jupiter.
Surprise on Jupiter
Precisely the atmosphere of Jupiter has given a surprise. It turns out that its clouds have a high enough concentration of water and a suitable temperature that, in theory, Extremophilic organisms would survive. "I am not suggesting that there is microbial life on Jupiter because it would have to have other requirements as well, such as the presence of the right nutrients, and
it is not enough that there is water and the right temperature, but this is an unexpected and exciting result."
clarifies Hallsworth, a researcher at Queen's University Belfast.
His colleague María Paz Zorzano, co-author and researcher at the Center for Astrobiology (CAB / CSIC-INTA) agrees, recalling that "
Jupiter is a hostile environment for life for other reasons
.
"
As detailed to ELMUNDO through an email, this planet "
has many other parameters that make it uninhabitable
and that we have not analyzed in this study, including radiation."
All known forms of life, this Spanish scientist enumerates, "need, in addition to availability of carbon, hydrogen, oxygen, nitrogen, phosphorus and sulfur, water at a sufficiently high level. The other critical factor is temperature. Finally, for the life proliferates it is necessary to be protected from radiation ", he sums up.
Data obtained on Venus
At the same press conference in which Hallsworth participated, co-author Chris McKay, from NASA's AMES Research Center, regretted their results for what they imply in the search for life outside the Earth since they would knock down the possibility that there are organisms in the clouds of Venus, but he highlighted the reliability of the sources used to measure water molecules: "
We have not used models, but data from direct observations
of pressure, temperature and water concentration made in the atmosphere of Venus by missions that have explored it, and that the ships that NASA is going to send in the next few years will repeat again ".
Illustration of Jupiter's clouds based on data taken by the 'Juno'NASA / JPL-Caltech / SwRI / MSSS / Gerald Eichstädt / Heidi N. Becker / Koji Kuramura probe
As Hallsworth recalls, for decades scouting missions have searched for traces of life outside of Earth in places where there are or were large bodies of water, such as rivers and lakes.
This was being done from February rover
Perseverance
NASA explores an area -e
l
crater of Mars Jezero is believed that housed a lake.
However, for the authors of this new work, the most important thing for life to be viable is not the amount of water, but the effective concentration of water molecules, which they call the term water
activity
or water
activity.
Water activity is measured on a scale of 0 to 1, and is equal to the relative humidity in a planet's atmosphere.
Laboratory studies have determined that for an organism to survive and reproduce it needs at least an activity of 0.585.
On Venus, the value obtained was 0.004, more than a hundred times less than what would be needed.
In the clouds of Mars a result of 0.537 was obtained, slightly below the necessary range, while in the atmosphere of Jupiter it was obtained 0.585, with a temperature between -10 and 40 ºC.
"Our research shows that the water in Venus' sulfuric acid clouds is insufficient to support active life,"
says Hallsworth.
Could it then be ruled out that there might be life in the clouds of Venus or is there still a possibility?
"The only forms of life that we can investigate are those that exist on Earth, and based on them is how we have defined life.
With current knowledge, talk about whether or not there is something that is capable of reproducing
, maintaining genetic information , metabolizing etc. in radically different conditions
would be a purely speculative exercise, "
says María Paz Zorzano.
For his part, the head of the CSIC Research Group on Meteorites and Planetary Geosciences, Jesús Martínez-Frías, not linked to this study, considers that the work of
Nature Astronomy
is
"Very interesting from the point of view of the detailed analysis of the importance of water activity in various planetary atmospheres, in relation to habitability". However, from his point of view, "the article is so focused on highlighting the relevance of a single parameter such as water activity, that it dispenses with many other variables that interact in a conjugated way in the definition of the concept of planetary habitability" .
"As a planetary geologist and astrobiologist, I am surprised that when talking about Jupiter it is omitted or excluded from mentioning the importance that for the origin and emergence of life - at least as we know it on Earth; so far the only known - have the mineral and rocky substrates and the geological processes that contributed to the physical-chemical interactions that generated the passage from the abiotic to the biotic ".
Missions to Venus
María Paz Zorzano considers "excellent news" that in the coming years an ESA and two NASA spacecraft will explore Venus, as "they will help us better understand its atmosphere and validate chemical models and remote sensing methods. This will ultimately serve to understand other Venus-like exoplanets orbiting other stars. " Precisely the approach used for this research, say its authors, could be applied to study the habitability of extrasolar planets.
To know if we are alone in the universe, Zorzano adds, "we must explore the habitable and the most extreme environments.
We must understand the Sun, and its interaction with the planets, study the comets that carry water, the meteorites that carry carbon and analyze the atmospheres that form. Only then can we extrapolate to other stars and exoplanets. "
According to this researcher, "the next targets to search for life outside the Earth are Mars and icy satellites like Europa".
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