Mars is a world marked by dramatic landscapes and few regions showcase this better than Acheron Fossae, a spectacular network of deep cracks and valleys that slice through the red planet's surface like ancient scars. Recent images from the European Space Agency's Mars Express spacecraft reveal the western edge of this fascinating geological formation, offering new insights into Mars's violent past and changing climate.

Image of Mars captured by the Hubble Space Telescope between April 27 and May 6, 1999, when Mars was 87 million kilometres from Earth

(Credit : NASA/ESA)

Acheron Fossae is an extensive system of deep, fault like cracks (known as fossae), with alternating chunks of raised and lowered ground, a pattern geologists call "horst and graben." Picture a broken chocolate bar where some pieces have been pushed up while others have dropped down, creating a jagged landscape of ridges and valleys that can be hundreds of kilometers long and several kilometers deep.

These features weren't created overnight. Likely dating back over 3.7 billion years to when Mars was most geologically active, such a pattern was created as hot material rose upwards beneath the martian crust. As molten rock pushed upward from deep within Mars, it stretched and cracked the planet's surface creating the deep valleys we see today.

Image of Acheron Fossae in Tharsis region on Mars

(Credit : NASA)

What makes Acheron Fossae particularly intriguing isn't just how it formed, but how it continues to change. The valley floors are relatively smooth, marked by gently weaving lines reminiscent of a flowing river. Rather than water, these valleys have been filled by a slow, viscous flow of ice rich rock, a lot like the rock glaciers we see here on Earth.

These Martian rock glaciers act like geological time capsules, preserving evidence of the Martian climatic history. Rock glaciers are very sensitive to changes in climate, and so act as good markers for how a planet's environment has changed over time. Here, they indicate that this region of Mars has experienced alternating periods of cool and warm, freeze and thaw.

The key to understanding these climate swings lies in Mars's unstable tilt. Unlike Earth, which maintains a relatively steady tilt thanks to the Moon's stabilising influence, Mars wobbles dramatically over time. Mars's tilt has swung between 15 and 45 degrees in the last 10 million years, while Earth's has varied between 22 and 24.5 degrees.

These variations, known as the Milankovitch cycles, create alternating ice ages and warm periods on Mars. During extreme tilts, ice can creep near to the planet's equator before shrinking back to its poles during warmer periods.

The images also reveal how erosion has transformed the landscape over millions of years. To the right of the main fossae, the deep cracks transition into flat, dark lowland plains, with a strip of raised mounds and rocky hills in between. These are the remains of what was once a continuous rock layer that has been slowly worn away by flows of ice and rock over time, leaving behind rounded hills called knobs and flat topped plateaus called mesas.

This erosion process creates a distinctive transition visible in the topographical data, from the deep red and yellow tones of higher ground gradually melting into light and darker blues indicating lower elevations. It's like watching a mountain range slowly dissolve into a plain over geological time.

Illustration of ESA's Mars Express spacecraft

(Credit : NASA/JPL)

These remarkable insights come courtesy of ESA's Mars Express spacecraft, which has been capturing and exploring Mars's landscapes since 2003. Using its High Resolution Stereo Camera, the orbiter has mapped the planet's surface in unprecedented detail, colour, and three dimensions for over two decades.

As we continue studying Mars, features like Acheron Fossae serve as natural laboratories for understanding planetary geology and climate evolution. They remind us that planets are dynamic systems, constantly changing over geological time scales. For future Mars missions, both robotic and human, understanding these processes will be crucial for navigation, resource utilisation, and safe exploration of our planetary neighbour.

Source : 

• When Martian Ground Falls Apart

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Searching for life on Mars has been an explicit goal of the astrobiological community for decades. However, they have not really had the resources to effectively do so, and they might be running out of time. Crewed missions to Mars are planned for as little as 15 years from now (though those timelines might be changing…again), and by the time that happens it may be too late to separate Martian life from unintentionally transplanted Earth-life. According to a group of researchers from the Agnostic Life Finding Association, there is one final chance to detect Martian life before it is irreversibly contaminated - the Mars Life Explorer (MLE). But to do its job properly, it’s going to need an upgrade.

MLE itself isn’t even a completely funded mission yet. Its objective would be to fly to Mars in the 2030s and search for signs of extant (not ancient) life, mainly by using a drill to drill into some water ice that exists near to the surface at a mid-latitude range on the Red Planet and analyzing that water sample for biological molecules.

It wouldn’t be the first experiment to try to capture those molecules, though. The Viking landers, which landed on Mars almost 50 years ago, also tried to capture biological materials, and provided famously ambiguous results. To this day, there is still debate among the scientific community as to whether or not Viking found life on Mars, yet no one has followed up the ambiguous Label Release experiment it performed with another one.

Enter MLE - the express intent of the Mars Life Explorer is in the name. But, according to a new paper from Gabriella Rizzo and Jan Spacek of the Agnostic Life Finding Association (ALFA), its current suggested suite of equipment would only look at the current habitability of Mars, rather than finding any evidence of actual life. More specifically, it would be limited to finding only life like that which appears on Earth. The authors point out that “research in ultra-low-biomass ecosystems on Earth, such as hyper-arid deserts and high-UV environments, has shown that instruments traditionally used in astrobiology often lack the sensitivity needed to detect life under such extreme conditions.”

In other words, the systems that we have previously put in place, and those planned for the MLE, won’t do their job correctly. MLE’s suite of instruments both won’t find life at extremely low concentrations, but it also won’t be able to deal with any life that doesn’t have a biochemistry similar to ours. Assuming there are large amounts of biochemically similar life on Mars are two very large assumptions that the ALFA team hope to eliminate.

Their suggestion is known as the Agnostic Life Finder (ALF), which was originally developed up to a Technology Readiness Level 4, meaning they’ve built a bench-top prototype, by a NASA Institute for Advanced Concepts grant. The ALF itself uses a system of chambers, filters, and an electric charge to separate organic molecules, which are charged, and large, from other potential components in a liquid environment, such as ions or non-charged particulates.

Cross contamination might not be the only reason Earth life could exist on Mars - as Fraser explains, detecting natural cross contamination can only be done prior to human presence.

According to the paper, the best use case for the ALF would be in a tank where massive amounts of Martian water is collected before the first crewed missions. This water collection is widely considered to be a necessary step in the development of a permanent Martian presence, but its unclear when, or if, either the private space companies that seem best placed to do so first, or a government space agency that decides to take that first leap, will prioritize building such a water capture and storage system. In the meantime, joining the payload of MLE, which isn’t necessarily going to the same place as future astronauts might, is the best bet for the system.

Given the budget cuts that are happening throughout NASA, it is unclear at this point whether MLE is even going to be funded at all, despite being one of the highest priority suggestions in the latest Planetary Decadal Survey. While the ALF itself is a relatively simple instrument, it does need to get to Mars somehow, and until it finds a ride the best the ALFA team can do is continue testing and development. But maybe some day someone will pick up the idea and give it a chance to answer one of the most important questions in astrobiology once and for all.

Learn More:

• G. Rizzo & J. Spacek - Enhancing Mars Life Explorer (MLE) with True Agnostic Life Detection Capabilities ALFA
• UT - How Likely Is Life on Mars?
• UT - Searching for Life on Mars in the Snow and Ice
• UT - Resources on Mars Could Support Human Explorers

Earth's magnetic field acts like an invisible shield, protecting our planet from harmful cosmic radiation that would otherwise strip away our atmosphere and make life nearly impossible. Unlike Mars, which lost most of its magnetic protection and now faces constant bombardment from space particles, Earth has maintained this critical defence system for billions of years.

Artist impression of the interior structure of the Earth

(Credit : CharlesC)

But how did this protective field form, and could it have existed when our planet was much younger? New research from scientists at ETH Zurich and Southern University of Science and Technology in China provides answers that fundamentally reshape our understanding of early Earth.

It’s long been understood that Earth's magnetic field comes from what's called the "dynamo effect." Deep inside our planet, the liquid iron and nickel core slowly cools over time, creating circular currents of flowing metal called convection currents. As Earth rotates, these currents twist into screw-like patterns, generating electric currents that produce our magnetic field.

Illustration of the dynamo mechanism that generates the Earth's magnetic field: convection currents of fluid metal in the Earth's outer core, driven by heat flow from the inner core, organised into rolls by the Coriolis force, generate circulating electric currents, which supports the magnetic field

(Credit : Andrew Z Colvin)

However, there was a significant gap in this theory. About one billion years ago, Earth's inner core began to crystallise and solidify. Before that time, the entire core was completely liquid. The big question was whether this fully liquid core could have generated the magnetic field necessary to protect early life.

The research team developed computer models to simulate whether a completely liquid core could generate a stable magnetic field, using calculations performed on the Piz Daint high-performance computer. What made their study particularly interesting was their ability to minimise the influence of the Earth's core viscosity to negligible levels, something no previous research had achieved. Their simulations demonstrated though that Earth's magnetic field could indeed have been generated billions of years ago in much the same way it operates today.

"Until now, no one has ever managed to perform such calculations under these correct physical conditions.” - lead author Yufeng Lin from the Southern University of Science and Technology in China.

This discovery has far reaching implications for our understanding of how life developed on Earth. Billions of years ago, life apparently benefited from the magnetic shield, which blocked harmful radiation from space, making its development possible in the first place. Without this protection, the it’s believed that the intense radiation would have made Earth's surface far too hostile to the delicate chemical processes that eventually led to living organisms.

The magnetic field essentially gave life on Earth a head start, creating a safer environment where complex molecules could form and evolve without being constantly disrupted by high energy particles from space.

Understanding Earth's magnetic field isn't just about ancient history, it’s crucial for our modern world. The magnetic field plays a crucial role in making satellite communications and many other aspects of modern civilisation possible. GPS systems, power grids, and communication networks all depend on this invisible shield. However, the field has flipped its polarity thousands of times throughout Earth's history, and scientists have recently observed rapid shifts in magnetic north's position. By gaining a better understanding about how the magnetic field works, researchers can make more accurate predictions about future changes and future flips that might affect our technology dependent society.

Source : 

• A fully liquid Earth’s core also generates a magnetic field

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When low-mass stars approach the end of their main-sequence phase, they expel clouds of gas that expand to form planetary nebulae. Since they were first identified in the late 1700s, astronomers have identified nebulae of all shapes and sizes, with most appearing circular, elliptical, or bipolar. However, some nebulae stray from this pattern, including the NGC 6072 nebula located about 3,060 light-years away in the southern constellation Scorpius. In a new series of high-resolution images taken by the James Webb Space Telescope (JWST), astronomers have noted some peculiar patterns that could provide insight into the lifecycle of stars.

At first glance, the images taken using Webb's Near-Infrared Camera (NIRCam) and Mid-Infrared Instrument (MIRI) suggest that NGC 6072 is a giant mess reminiscent of a bug splattered on a windshield. However, the structure traced by Webb's instruments suggests that some very complex mechanisms are at work within it. The NIRCam data shows a hot central core region glowing brightly with a light blue hue, surrounded by elliptical outflows that give it a multi-polar configuration. These outflows have resulted in two lobes of gas and dust that cross the center at near-vertical angles, while a third extends perpendicularly to form an equatorial plane.

The central region covers a large area of dark pockets surrounded by orange material that grows redder the farther it is from the center. This is consistent with the gas and dust growing colder the farther it ventures from the hot central core. The three-lobe structure could mean that at least two stars are at the nebula's center, likely consisting of a younger companion to the aging star that has already lost most of its material. The MIRI data, meanwhile, captures the longer-wavelength infrared data, which emphasizes the web-like structure created by the outflows of dust.

The NGC 6072 nebula as imaged by Webb's MIRI instrument.

Credit: NASA/ESA/CSA/STScI

This image also reveals the star that could be central to the nebula (which appears as a pinkish-white dot), as well as concentric rings expanding from the central region to the edges of the lobes. This could also be evidence of a secondary star at the center, orbiting the older star and carving out rings in its wake. Alternately, the rings could have been caused by pulsations in the outflows, where gas and dust were expelled at long intervals (every thousand years or so) in all directions. The areas represented by NIRCam (red) and MIRI (blue) both trace the cool gas in the cloud (likely molecular hydrogen), while the central regions trace hot ionized gas.

As the aging star at the center cools, the nebula will dissipate into the interstellar medium (ISM), contributing the heavier elements from which new stars and planetary systems will form. The study of planetary nebulae is a major objective for the JWST, which will provide new insights into the lifecycle of stars and their impact on the surrounding environments. These studies could also shed light on what may become of our Sun when it reaches the end of its main sequence phase, billions of years from now.

Further Reading: 

• Webb Space Telescope

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