Planet Mars animation.
May 8, 2021
Image above: We keep sending missions to Mars with the key objective to search for past or present life. But what if a huge impact early in the Red Planet’s history hindered any future possibility for life to thrive?
Recent studies into the Martian “crustal dichotomy” indicate the planet was struck by a very large object, possibly a massive asteroid. Now researchers believe that this same impact may have scrubbed any chance for life on Mars, effectively making the planet sterile. This asteroid may have penetrated the Martian crust so deep that it damaged the internal structure irreparably, preventing a strong magnetic field from enveloping the planet. The lack of a Mars magnetosphere thereby ended any chance for a nurturing atmosphere…
Mars looks odd. Early astronomers noticed it, and today’s observatories see it every time they look at the red globe. Mars has two faces. One face (the northern hemisphere) is composed of barren plains and smooth sand dunes; the other face (the southern hemisphere) is a chaotic, jagged terrain of mountains and valleys. It would appear the crustal dichotomy formed after a massive impact early in the development of Mars, leaving the planet geologically scarred for eternity. But say if this impact went beyond pure aesthetics? What if this planet-wide impact zone represents something a lot deeper?
Planet Mars
To understand what might have happened to Mars, we have to first look at the Earth. Our planet has a powerful magnetic field that is generated near the core. Molten iron convects, dragging free electrons with it, setting up a huge dynamo outputting the strong dipolar magnetic field. As the magnetic field threads through the planet, it projects from the surface and reaches thousands of miles into space, forming a vast bubble. This bubble is known as the magnetosphere, protecting us from the damaging solar wind and prevents our atmosphere from eroding into space. Life thrives on this blue planet because Earth has a powerful magnetic solar wind defence.
Video above: Mars 101 / Recent NASA exploratory expeditions revealed some of the red planet's biggest mysteries. This video explains what makes it so different from Earth and what would happen if humans lived there.
Although Mars is smaller than Earth, scientists have often been at a loss to explain why there is no Martian magnetosphere. But according to the growing armada of orbiting satellites, measurements suggest that Mars did have a global magnetic field in the past. It has been the general consensus for some time that Mars’ magnetic field disappeared when the smaller planet’s interior cooled quickly and lost its ability to keep its inner iron in a convective state. With no convection comes a loss of the dynamo effect and therefore the magnetic field (and any magnetosphere) is lost. This is often cited as the reason why Mars does not have a thick atmosphere; any atmospheric gases have been eroded into space by the solar wind.
However, there may be a better explanation as to why Mars lost its magnetism. “The evidence suggests that a giant impact early in the planet’s history could have disrupted the molten core, changing the circulation and affecting the magnetic field,” said Sabine Stanley, assistant professor of physics at the University of Toronto, one of the scientists involved in this research. “We know Mars had a magnetic field which disappeared about 4 billion years ago and that this happened around the same time that the crustal dichotomy appeared, which is a possible link to an asteroid impact.”
Internal Models of Mars - Data by SEIS / Mars InSight
During Mars’ evolution before 4 billion years ago, things may have looked a lot more promising. With a strong magnetic field, Mars had a thick atmosphere, protected from the ravages of the solar wind within its own magnetosphere. But, in an instant, a huge asteroid impact could have changed the course of Martian history forever.
“Mars once had a much thicker atmosphere along with standing water and a magnetic field, so it would have been a very different place to the dry barren planet we see today.” – Monica Grady, professor of planetary and space sciences at the Open University.
Losing its magnetic field after the deep asteroid impact catastrophically damaged the internal workings of the planet, Mars quickly shed its atmosphere, thereby blocking its ability to sustain life in the 4 billion years since. What a sad story...
Impacted by an massive iron asteroid like 16 Psyche?
The red surface of Mars composed of iron oxide is probably the consequence of an impact of an iron asteroid or an direct impact of a huge asteroid which on its impact created a over pressure of the core of Mars and gave rise to the volcanoes which lie in it other side, these "spat out" some of the molten metal from the core mixing with the asteroid which fell as dust all over the planet's surface.
Artist's view of Olympus Mons eruption
Valles Marineris could be the result of the over pressure of the core of Mars, causing a large crack (Valles Marineris) in its surface.
Valles Marineris (Click on the image for enlarge)
What also explains the gigantic size of volcanoes on Mars, like Olympus Mons is that there is no plate tectonics like on Earth, on Mars.
No plate tectonics like on Earth, on Mars
Two Faces of Mars Explained
Mars has two faces. No, not those kind of faces, but the notable differences between the northern and southern hemisphere. Mars has lowlands in the north and highlands in the south. This disparity has long puzzled planetary scientists, but most concurred that early in Mars history, impacts shaped the planet’s two-faced landscape. But many disagreed whether several small impacts or one big one were responsible for sculpting Mars surface. Now scientists at the California Institute of Technology have shown through computer modeling that the Mars dichotomy, as the divided terrain has been termed, can indeed be explained by one giant impact early in the planet’s history.
“The dichotomy is arguably the oldest feature on Mars,” said Oded Aharonson from Caltech. Scientists believe the differences in hemispheric features arose more than four billion years ago.
Previously, scientists discounted the idea that a single, giant impactor created the lower elevations and thinner crust of Mars’s northern region, says Margarita Marinova, a graduate student at Caltech, and one of the lead authors of the study.
For one thing, Marinova explained, it was thought that a single impact would leave a circular footprint, but the outline of the northern lowlands region is elliptical. There is also a distinct lack of a crater rim: topography increases smoothly from the lowlands to the highlands without a lip of concentrated material in between, as is the case in small craters. Finally, it was believed that a giant impactor would obliterate the record of its own occurrence by melting a large fraction of the planet and forming a magma ocean.
“We set out to show that it’s possible to make a big hole without melting the majority of the surface of Mars,” Aharonson says. The team modeled a range of projectile parameters that could yield a cavity the size and ellipticity of the Mars lowlands without melting the whole planet or making a crater rim.
The team ran over 500 computer simulations combining various energies, velocities, and impact angles. Finally, they were able to narrow in on a “sweet spot”–a range of single-impact parameters that would make exactly the type of crater found on Mars. Their dedicated supercomputer allowed them to run simulations not run in the past. “The ability to search for parameters that allow an impact compatible with observations is enabled by the dedicated machine at Caltech,” Aharonson said.
The favored simulation conditions outlined by the sweet spot suggest an impact energy of around 1029 joules, which is equivalent to 100 billion gigatons of TNT. The impactor would have hit Mars at an angle between 30 and 60 degrees while traveling at 6 to 10 kilometers per second. By combining these factors, Marinova calculated that the projectile was roughly 1,600 to 2,700 kilometers across.
Rare metals on Mars and Earth implicate colossal impacts
Estimates of the energy of the Mars impact place it squarely between the impact that is thought to have led to the extinction of dinosaurs on Earth 65 million years ago and the one believed to have extruded our planet’s moon four billion years ago.
Marinova said the timing of formation of our moon and the Mars dichotomy is not coincidental. “This size range of impacts only occurred early in solar system history,” she says. The results of this study are also applicable to understanding large impact events on other heavenly bodies, like the Aitken Basin on the moon and the Caloris Basin on Mercury.
This report, published in the June 26 issue of Nature, goes along with two other papers on the Mars dichotomy. One published by Jeffrey Andrews-Hanna and Maria Zuber of MIT and Bruce Banerdt of JPL examine the gravitational and topographic signature of the dichotomy with information from the Mars orbiters. Another accompanying report, from a group at UC Santa Cruz led by Francis Nimmo, explores the expected consequences of mega-impacts.
Related links:
The case for life on Mars | International Journal of Astrobiology:
https://www.cambridge.org/core/journals/international-journal-of-astrobiology/article/abs/case-for-life-on-mars/CB153AA2DEDFB4EA31B6E8F4C7AC4E58
Life on Mars? | Science | Smithsonian Magazine:
https://www.smithsonianmag.com/science-nature/life-on-mars-78138144/
(PDF) Magnetism, Iron Minerals, and Life on Mars
https://www.researchgate.net/publication/6978389_Magnetism_Iron_Minerals_and_Life_on_Mars
Signs of Past Life on Mars?
https://mars.nasa.gov/MPF/martianchronicle/martianchron7/signs.html
2 The Present State of Knowledge About Mars and Possible Life
https://www.nap.edu/read/11937/chapter/4
Images, Animations, Video, Original News Source & Data: Times Online (UK)/EurekAlert/National Geographic/NASA/JPL-Caltech/ESA/Orbiter.ch Aerospace/Roland Berga.
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