Could Mars and Venus be just like Earth in the past?
Mars and Venus are the two closest and most Earth-like planets in size and distance from
the sun.
The most recent research has shown the existence of water on Mars, and simulations of the climatic
evolution of Venus indicate that it could also have had water in the past, being so.
Mars and Venus, were planets with oceans and forests full of life like Earth millions of
years ago?
Let's find out!
" In
a
past video, we talked about what all the planets in the solar system looked like billions of
years ago.
If you have not seen it, we recommend it.
In that video, we mentioned that in the past, Mars and Venus may have been very similar
to Earth, but how similar?
Could they have had all the necessary conditions to house living beings?
Let's start with Venus Billions of years ago, after the planets finished
forming, they were very different from how they are today; Earth was not the paradise
we know, Mars was not that cold, and Venus was not that hot.
In the case of Venus, it is possible that after it passed the "Late Bombardment Period,"
it maintained stable temperatures and hosted liquid water for billions of years before
an event triggered drastic changes in the planet.
Venus is a lifeless planet, with a toxic atmosphere 90 times thicker than ours and surface temperatures
reaching 464 C°.
These temperatures are hot enough to melt lead.
The scientific community often classifies Venus as Earth's twin because the two planets
are similar in size.
But besides that one aspect, they have nothing else in common.
However, a study by scientist Michael Way of the Goddard Institute for Space Sciences
compared five climate simulations from Venus' past.
Each scenario suggested that the planet could support liquid water and a temperate climate
on its surface for at least three billion years.
Those temperatures could have included a high of 50 degrees Celsius and a low of 20 degrees
Celsius, which is enough to keep liquid water in its atmosphere.
But about 750 million years ago, something triggered the release of carbon dioxide from
the planet's rocks, transforming its climate, evaporating all the water, and turning it
into a planet without water or life.
According to Michael Way, the hypothesis is that Venus may have had a stable climate for
billions of years.
The near-global resurgence event may be responsible for its transformation from an Earth-like
climate to the hellish greenhouse we see today.
How did the idea that Venus could be like Earth come about?
NASA's Pioneer mission first suggested the idea that Venus may have oceans of water in
the 1980s.
But given its location as the second planet from the sun, Venus was not considered conducive
to sustaining an ocean.
Venus receives more sunlight than Earth, which evaporates liquid water, sending hydrogen
into space and trapping a buildup of carbon dioxide.
That would lead to a continuous greenhouse effect that would create its current toxic
atmosphere.
Images of Venus taken by the Venera 9 probe shows that Venus's topography was entirely
altered by volcanic eruptions that most likely filled lowland regions and possible ocean
basins over the past billion years.
Simulating the past Many of the tools we use to model climate
change on Earth can be adapted to study climates on other planets, both past, and present,
said Michael Way, a GISS researcher and lead author of the paper.
Research on this finding was conducted as part of NASA's Planetary Astrobiology program
through the Nexus for Exoplanet System Science (NExSS) program, which searches for life on
planets orbiting other stars, or exoplanets, combining intuitions from the fields of astrophysics,
planetary science, heliophysics, and Earth sciences.
Scientists have theorized that Venus formed from ingredients similar to Earth's but followed
a different evolutionary path.
Of the five simulations performed, three included the current topography of Venus.
They added a deep ocean of about 310 meters, a shallow ocean of about 10 meters, and traces
of water on the ground.
The researchers compared this to two other simulations, one using Earth's topography
with a deep ocean and an ocean world.
To recreate the likely conditions on Venus that occurred 4.2 billion years ago and then
simulate the changes over time, scientists gradually increased solar radiation to reflect
the sun as it warmed.
This also changed atmospheric conditions over time.
Previously, researchers believed that Venus was too close to the sun to hold liquid water
on its surface, beyond the inner limit of the sun's habitable zone.
The new simulations change that belief.
Venus currently has almost twice the solar radiation we have on Earth.
However, in all the modeled scenarios, it was discovered that Venus could still withstand
surface temperatures that could retain liquid water.
Simulations suggest that Venus underwent a rapid cooling phase a few billion years after
its formation.
Then, the atmosphere would have been filled with carbon dioxide.
If Venus evolved in a similar way to Earth, that carbon dioxide would have descended from
the atmosphere, attracted by silicates, and would have been trapped on the surface.
This would have allowed the atmosphere to be filled with nitrogen with small amounts
of carbon dioxide and methane, providing stability.
This would indicate that for at least 2 billion years, Venus had the necessary conditions
to host liquid water, oceans, and possibly living beings.
But something happened about 700 million years ago that remains a mystery, although researchers
think it's related to volcanic activity.
The magma released the carbon dioxide trapped in the soil and released into the atmosphere,
and when the magma cooled, the gas could not be reabsorbed on the surface and was scattered
in the air.
So much carbon dioxide in the atmosphere caused a runaway greenhouse effect that transformed
the planet quickly and went from a paradise with oceans of water to a planet with a deadly
and toxic atmosphere.
Mars suffered the same fate Like Venus, Mars has likely been like Earth,
but in the case of Mars, much more substantial evidence has been found both on its surface
and in its atmosphere.
How was it possible for Mars to host oceans if the Red Planet is farther from the Sun
than Earth, and billions of years ago, it sun-generated less heat than today?
This is something that keeps Timothy Lyons up at night.
He is a professor of biogeochemistry at the University of California, Riverside, and one
of the main researchers on the evolution of the atmosphere of Mars.
For Mars to be warm enough to host liquid water, its atmosphere would likely have needed
an immense amount of greenhouse gases, especially carbon dioxide said UCR graduate student Chris
Tino, co-author of the paper with Eva Stüeken, a professor at the University of St. Andrews
in Scotland.
Since it is impossible to sample the atmosphere of Mars just as it was ago billions of years
ago to know its carbon dioxide content, the team looked for a place on Earth whose geology
and chemistry bear remarkable similarities to the Martian surface and which could provide
some of the missing pieces.
This place is the crater Nordlinger Ries of southern Germany.
Formed approximately 15 million years ago after being hit by a meteorite, Ries Crater
features some of Earth's best-preserved rock and mineral layers.
For its part, NASA's Mars rover analyzed at the beginning of 2020 an ancient crater with
an identical and well-preserved structure on the red planet.
Both places presented liquid water in their distant past, so comparing their chemical
composition brings new and valuable information to what we already have.
Although according to Tino, it is doubtful that ancient Mars had enough oxygen to harbor
complex life forms, some microorganisms could have developed if ancient Martian water had
had a neutral pH level and been highly alkaline.
Those conditions involve enough carbon dioxide in the atmosphere to warm the planet and make
liquid water possible, perhaps thousands of times more than Earth's atmosphere has today.
The evidence is there Unlike Venus, which it has been concluded
that it was like Earth only by climatic simulations, in the case of Mars, there is physical and
observable evidence that indicates the bodies of water on the planet.
Today the atmosphere of Mars is estimated to have 0.01% water in the form of vapor,
and it is known that there is also water ice in the subsurface.
In July 2018, Italian researchers from the European Space Agency's (ESA) Mars Express
mission announced the detection of an underground lake on Mars.
Due to the climate of the red planet, liquid water can't be on its surface, so the only
possibility is to find it locked in the subsoil.
With about 20 kilometers in diameter and 1.5 kilometers deep under the Martian South Pole
ice, this lake's presence has been interpreted thanks to the veteran MARSIS radar, operational
since 2005, which has been readjusted to increase its sensitivity.
Andrea Cicchetti, director of operations at MARSIS, said radar sampling rates and data
resolution were too low.
They had to devise new software to generate more extensive sampling and improve the resolution
of the data collected.
"Now we see things that weren't possible before," Cicchetti said.
However, it is still not easy.
The mass of water detected is rich in salts, a key element to keep it in a liquid state
(the salt in the water lowers the freezing point) where temperatures touch 70 ° C below
zero.
This finding opens the door to discovering other bodies of water in other places on the
planet, which in turn leads to rescuing the million-dollar question again: is there life
on Mars?
If there is, it could be found in microbial form swimming in those frigid Martian waters.
Everything indicates that, sooner rather than later, the riddle will be solved.
For many years the red planet has been thoroughly scrutinized.
The first probes to approach it did so in the 1960s.
Since then, rovers and satellites of all kinds are revealing their mysteries.
Until now, samples of large amounts of water in the subsurface, traces of what may have
been water currents etched into the rocks and slopes of the planet's surface, as well
as formations indicating the presence of ancient water currents, indicate that most likely
in the past Mars was like Earth.
Vast oceans full of water covered much of the planet, a much denser and heavier atmosphere
full of carbon dioxide, and large lakes flooded the entire landscape.
With all these conditions, it is possible that Mars could be the cradle that gave rise
to living beings at some point in history.
Then, the impact of a meteorite expelled that organic material taking her to earth.
In that case, all living beings on this planet would be extraterrestrials brought by the
power of meteorite impacts; this is what we know as "The theory of panspermia."
While there is no way to prove this, it is interesting to know that our planetary neighbors
in the past may have been paradises for life, but something happened that caused them to
cease to be.
Today Mars is nothing like what perhaps it was in the past; the most accepted hypotheses
maintain that at some point in history, the magnetic field of the planet was weakening
until slowly disappearing completely; this left the atmosphere exposed to solar Radiation,
which tore off the atmosphere, taking most of the water in the form of steam and the
rest was deposited under the subsoil where the Radiation from the sun cannot evaporate
it.
Mars and Venus may have been like Earth billions of years ago, but they are no longer.
Both planets are a reminder that Earth won't always be the paradise it is today; chances
are that our blue home will resemble one of these two planets in the future.