# Is the wind's intensity on Mars similar to Earth?

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I've read that in Mars' poles, the winds can be as fast as 400 km/h, when the poles are exposed to sunlight because the frozen $CO_2$ sublimes. I know that the Martian atmosphere is much thinner than Earth's atmosphere.

So, by knowing the wind speeds on Mars, is there any way to get an idea of its intensity, or in other words, the intensity of a wind of x speed in Mars, to which speed of wind of Earth is comparable, for them to have the same intensity?

Credit to this question for inspiration, though my calculation methods differ.

The dynamic pressure equation is $$q=0.5 ho v^2$$ where $$q$$ is the pressure, $$ho$$ is the atmospheric density, and $$v$$ is the wind speed. If we want to know what wind speeds give us equivalent pressures on Earth and Mars, we simply generate dynamic pressure equations for each of them: $$q=0.5 ho_e v_e^2$$ and $$q=0.5 ho_m v_m^2$$, set them equal $$q=0.5 ho_e v_e^2=0.5 ho_m v_m^2$$, and solve for $$v_e$$ to get $$v_e=sqrt{frac{ ho_m}{ ho_e}}v_m$$ where $$ho_m=0.020 space kg/m^3$$ is the atmospheric density for Mars, $$ho_e=1.225 space kg/m^3$$ is the atmospheric density on Earth, $$v_m$$ is the wind speed on Mars, and $$v_e$$ is the equivalent wind speed on Earth.

With a velocity ratio of about 7.826 we can plug in a few values for wind speed in kilometers per hour for Mars to get:

v_mars v_earth equivalent 10 1.28 50 6.39 100 12.8 200 25.6 400 51.1

These could be kph, or in fact, any units of velocity. screeenshot

and here's what hat looks like in a plot:

So the 400 kph gust on Mars only has equivalent pressure of a 51 kph gust here on Earth

## The Fact and Fiction of Martian Dust Storms

This artists concept illustrates a Martian dust storm, which might also crackle with electricity.
Credit: NASA

Andy Weir's "The Martian" begins with a massive dust storm that strands fictional astronaut Mark Watney on Mars. In the scene, powerful wind rips an antenna out of a piece of equipment and destroys parts of the astronauts' camp.

Mars is infamous for intense dust storms, which sometimes kick up enough dust to be seen by telescopes on Earth.

"Every year there are some moderately big dust storms that pop up on Mars and they cover continent-sized areas and last for weeks at a time," said Michael Smith, a planetary scientist at NASA's Goddard Space Flight Center in Greenbelt, Maryland.

Beyond Mars' large annual storms are massive storms that occur more rarely but are much larger and more intense.

"Once every three Mars years (about 5 ½ Earth years), on average, normal storms grow into planet-encircling dust storms, and we usually call those 'global dust storms' to distinguish them," Smith said.

It is unlikely that even these dust storms could strand an astronaut on Mars, however. Even the wind in the largest dust storms likely could not tip or rip apart major mechanical equipment. The winds in the strongest Martian storms top out at about 60 miles per hour, less than half the speed of some hurricane-force winds on Earth.

Focusing on wind speed may be a little misleading, as well. The atmosphere on Mars is about 1 percent as dense as Earth's atmosphere. That means to fly a kite on Mars, the wind would need to blow much faster than on Earth to get the kite in the air.

"The key difference between Earth and Mars is that Mars' atmospheric pressure is a lot less," said William Farrell, a plasma physicist who studies atmospheric breakdown in Mars dust storms at Goddard. "So things get blown, but it's not with the same intensity."

Challenges of Solar Power

The deck of NASA's Mars Exploration Rover Spirit is so dusty that the rover almost blends into the dusty background in this image assembled from frames taken by the panoramic camera (Pancam) during the period from Spirit's Sol 1,355 through Sol 1,358 (Oct. 26-29, 2007).
Credit: NASA/JPL-Caltech/Cornell

"If you've seen pictures of Curiosity after driving, it's just filthy," Smith said. "The dust coats everything and it's gritty it gets into mechanical things that move, like gears."

The possibility of dust settling on and in machinery is a challenge for engineers designing equipment for Mars.

This dust is an especially big problem for solar panels. Even dust devils of only a few feet across -- which are much smaller than traditional storms -- can move enough dust to cover the equipment and decrease the amount of sunlight hitting the panels. Less sunlight means less energy created.

In "The Martian," Watney spends part of every day sweeping dust off his solar panels to ensure maximum efficiency, which could represent a real challenge faced by future astronauts on Mars.

Global storms can also present a secondary issue, throwing enough dust into the atmosphere to reduce sunlight reaching the surface of Mars.

When faced with a larger dust storm in the book, Watney's first hint is the decreased efficiency of his solar panels, caused by a slight darkening of the atmosphere. That's a pretty accurate depiction of what large dust storms can do, Smith said.

When global storms hit, surface equipment often has to wait until the dust settles, either to conserve battery or to protect more delicate hardware.

"We really worry about power with the rovers it's a big deal," Smith said. "The Spirit and Opportunity rovers landed in 2004, so they've only had one global dust storm to go through (in 2007) and they basically shut down operations and went into survival mode for a few weeks."

A towering dust devil casts a serpentine shadow over the Martian surface in this image acquired by the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter.
Credit: NASA/JPL-Caltech/University of Arizona

As sunlight hits the ground, it warms the air closest to the surface, leaving the upper air cooler. As in thunderstorms on Earth, the warm and cool air together become unstable, with warm air rising up and taking dust with it.

Rising plumes of warm air create everything from small dust devils, similar to those that form in deserts on Earth, to larger continent-sized storms. These larger storms sometimes combine into the global storms, which cover the entire planet in atmospheric dust.

Larger storms typically only happen during summer in Mars' southern hemisphere. Seasons on Mars are caused by the tilt of the planet, like on Earth. But Mars' orbit is less circular than Earth's for part of a Martian year, the planet is closer to the sun and therefore significantly hotter. This warmer time is during the southern hemisphere's summer, so radiative heat forces are strongest then. Once started, bigger storms can last weeks to months.

Scientists aren't really sure why the years' long gaps between storms exist.

"It could be that it just takes a while for the sources to replenish themselves," Smith said. "Maybe there's some kind of cycle that the dust has to go through to get back into the right places to trigger a new one, or maybe it's just kind of luck."

Scientists have been tracking these global dust storms on Mars for more than a century, using both telescopes on Earth and spacecraft orbiting Mars. The storms have been observed a number of times since 1909, most recently in 2007. Now, more than eight years later, Smith is hopeful he'll get the chance to study a major storm soon.

"We're overdue for a global dust storm and it could be saving up a really big one this year, so that would kind of fun," he said. "I like the dust storms."

## Warming up the Red Planet

Mars’ atmosphere is far too thin and cold to support liquid water on its surface. With an atmospheric pressure just 0.6% of Earth’s, any surface water would quickly evaporate or freeze, just as NASA’s Phoenix lander saw in 2008.

There are a few different schools of thought on how—or if—we could heat up Mars’ atmosphere and make it more hospitable to life. Elon Musk has suggested, for example, that we could terraform Mars by exploding nuclear bombs over its polar caps. He says that the radiation wouldn’t be an issue since the explosion would be in space over the poles, but the heat release would vaporize the frozen carbon dioxide to greenhouse warm the planet and melt the water ice.

Nuking Mars raises a host of scientific, ethical, and legal questions. From a scientific perspective, researchers estimate that the resulting melted water ice could easily cover the planet to a depth of a few tens of meters, but it probably wouldn’t last for long. The carbon dioxide added to Mars’ atmosphere by vaporizing the polar caps would only double the pressure, a far cry from the comparable pressure to Earth required for conditions warm enough to sustain surface liquid water and atmospheric water vapor.

Borealis Planitia - Mars Express Mars Express HRSC image of the Martian north polar region. This image captures the north polar cap, a bank of stratocumulus over Borealis Planitia and the highlands of Tempe Terra (left). This image was taken during Mars Express' 14,125th orbit of Mars, May 2, 2014. Image: ESA/DLR/FU Berlin/J. Cowart, CC BY-SA 3.0 IGO

Mars has more abundant sources of carbon dioxide, such as those locked in the martial soil and tightly bonded carbon in minerals. But based on 20 years of NASA and ESA satellite data, researchers estimate that even if we mine Mars’ entire surface for carbon dioxide, the atmospheric pressure would still only be about 10-14% of Earth’s. This would correspond to an average temperature rise of about 10 degrees Celsius––not nearly enough to sustain liquid water.

To put this all into perspective: we would need more carbon dioxide to meaningfully warm up Mars than humans have released throughout our entire history on Earth. Terraforming Mars is therefore a daunting endeavor that doesn’t seem possible with current technology.

With future technological advances, we might be able to excavate minerals deep in the Martian crust that may hold significantly more carbon dioxide and water. But the extent of these buried deposits isn’t currently known or evidenced by satellite data. We could also artificially introduce heat-trapping gases that are superior to carbon dioxide, like chlorofluorocarbons. These gases are short-lived, though, so the process would need to be repeated on a large scale to keep Mars warm.

Another idea is to import gases by redirecting comets and asteroids to hit Mars. However, this isn’t exactly practical, as it would require an inordinate amount of impacts to make any meaningful difference.

## Is the wind's intensity on Mars similar to Earth? - Astronomy

Among the scientific instruments on the Phobos spacecraft, one was expected to study the plasma and wave phenomena in the Martian environment: the Plasma-Wave System, PWS. Here we report on the PWS plasma and electric-field spectrum measurements during two Martian bow shock crossings by Phobos 2: one is located near the subsolar point and the other near the dusk terminator. A comparison is also made with the Earth's shock crossed by Phobos 1. As at Earth, three main regions were identified: the upstream region, the shock transition region and the downstream region. A shock foot boundary is often observed in front of the bow shock. This foot is known to be associated with gyrating ions reflected from the shock. Electric-field spectra are presented and tentatively interpreted. The dynamic spectrograms shown in this report differ from the ones published previously, for the fact that the filter channels are not sampled at the same time has been taken into account.

## Mars may look like an alien wasteland, but we now have more evidence it could have once been another Earth

There is a reason Perseverance landed where it did, and that reason goes back at least 3.5 billion years.

Early Mars is thought to have been Earthlike before solar radiation and cosmic other forces killed its atmosphere. This explains why the rover that has now gone viral in the Twitterverse and just about everywhere else touched down in Jezero Crater, which is thought to have once been a huge lake that could have also been crawling with microbial life. Scientists have now found evidence that Mars went through the same phase as Earth before both planets got their atmospheres — something that has not been proven until now.

#### More space

“On Earth, oxidation happened because of the evolution of oxygenic photosynthesis. On Mars, we do not see any evidence that anything like that occurred there,” planetary scientist Joseph Michalski, who coauthored a study recently published in Nature Astronomy, told SYFY WIRE. "Also, an oxidizing atmosphere does not imply abundant oxygen. It just means that the atmosphere could 'steal' electrons from other gases."

The timing for this discovery was right on. Perseverance has started searching the Red Planet for any potential signs of life, and that life — if it was anything like like as we know it — would have required an atmosphere. But wait. Before you can figure out around when Mars started get an atmosphere, and what it was like with an atmosphere (kind of hard to imagine looking at what is now a space desert), you have to back up further to before it even had an oxidized atmosphere. There is a time that things didn’t rust on Earth or Mars because there was not enough oxygen in the atmosphere to interact with substances rich in iron.

Instead of an oxidized atmosphere, both Earth and Mars once had a reduced atmosphere. This is not the same as the massive reduction in atmosphere the Red Planet experienced after most of its atmosphere was decimated by solar winds and other cosmic forces. A reduced atmosphere is made up of mostly reduced gases like methane, ammonia, and hydrogen sulfide, which are hydrogen-rich rather than oxygen-rich. Humans would not have been able to handle breathing in this poison. However, there are microorganisms that are fueled by methane right here on our planet, so it wouldn’t be impossible for Mars.

What made Mars habitable once was its own greenhouse effect. While greenhouse gases have been demonized on Earth because too much carbon dioxide and other types have been released into the atmosphere from human pollution, the right amount of these atmospheric gases is necessary to warming up a planet just enough so life-forms can thrive.

Rocks on Mars, as seen by Curiosity. Credit: NASA

"We used geological observations to confirm theoretical models of atmospheric properties. The results are significant because they demonstrate the viability of reduced gases such as methane or hydrogen for forming short term, strong greenhouses on Mars," Michalski said. "We have known for years that CO2 is unlikely to explain greenhouse warming on Mars. This work helps solve that mystery."

Previous studies had assumed that on Mars, this phenomenon happened with reduced gases instead of CO2, meaning the planet must have had a reduced atmosphere. Evidence of this was finally found by Liu and his team when they investigated spacecraft data of weathered Martian rocks that showed signs of having been exposed to such an atmosphere. So what could Perseverance possibly find in those rocks?

"It is possible that Perseverance will detect mineral assemblages within the putative lake sediments that would indicate reduced surface fluids," Michalski said.
"That would be an interesting test for our model. Eventually, the rover should climb out of Jezero crater onto the plains and explore more standard, ancient Noachian terrain (not just lake sediments). If we make it that far, those results will also be interesting for exploring ancient weathering patterns."

An orbiting spacecraft remotely examined rocks on the surface of Mars. This spacecraft was equipped with an instrument capable of infrared spectroscopy, which revealed the chemistry of these primordial rocks. When infrared light hits a target, it interacts with the molecules that make up that object. How the object in question absorbs, reflects or emits this light can give away what its chemical composition is like. What the researchers wanted to know was the composition of the paleosols on Mars, soils that formed eons ago and are physical and chemically unrelated to soils that formed more recently. This is how they identified a chemical sign of weathering caused by a reduced atmosphere.

Mars later underwent an oxidation event much the Earth’s Great Oxidation Event on Earth, though during a different time and possibly for different reasons. Earth’s atmosphere became oxidized because of oxygen was a by-product of processes like photosynthesis in early organisms. Proving that Mars had a reduced atmosphere before its oxidation event happened could mean life was somehow involved in the shift. Now that he has revealed more about the Red Planet's past, Michalski is going to be taking his research further in the future.

"We plan to apply this model to results from the Curiosity rover in Gale crater," he said. "We also are looking at the mineralogical evidence for climate transitions throughout the planet. There is an intresting story to be told, which we hope to tell very soon."

As Perseverence surveys Jezero Crater, it may find more to support this discovery ,and maybe even a fossilized microbe.

## 3 Things We've Learned From NASA's Mars InSight

NASA's InSight used its Instrument Context Camera (ICC) beneath the lander's deck to image these drifting clouds at sunset. This series of images was taken on April 25, 2019. Full Image Details

This illustration shows NASA's InSight spacecraft with its instruments deployed on the Martian surface. Full Image Details

Scientists are finding new mysteries since the geophysics mission landed two years ago.

NASA's InSight spacecraft touched down Nov. 26, 2018, on Mars to study the planet's deep interior. A little more than one Martian year later, the stationary lander has detected more than 480 quakes and collected the most comprehensive weather data of any surface mission sent to Mars. InSight's probe, which has struggled to dig underground to take the planet's temperature, has made progress, too.

There was a time when the surfaces of Mars and Earth were very similar. Both were warm, wet, and shrouded in thick atmospheres. But 3 or 4 billion years ago, these two worlds took different paths. The mission of InSight (short for Interior Exploration using Seismic Investigations, Geodesy and Heat Transport) has been to help scientists to compare Earth to its rusty sibling. Studying what the depths of Mars is made of, how that material is layered, and how quickly heat seeps out of it could help scientists better understand how a planet's starting materials make it more or less likely to support life.

While there's more science to come from InSight, here are three findings about our red neighbor in the sky.

Faint Rumblings Are the Norm

InSight's seismometer, which was provided by the French space agency, Centre National d'Études Spatiales (CNES), is sensitive enough to detect slight rumblings from great distances. But it wasn't until April 2019 that seismologists with the Marsquake Service, coordinated by ETH Zurich, detected their first marsquake. Since then, Mars has more than made up for lost time by shaking frequently, albeit gently, with no quakes larger than magnitude 3.7.

The lack of quakes larger than magnitude 4 poses something of a mystery, considering how frequently the Red Planet shakes due to smaller quakes.

"It's a little surprising we haven't seen a bigger event," said seismologist Mark Panning of NASA's Jet Propulsion Laboratory in Southern California, which leads the InSight mission. "That may be telling us something about Mars, or it may be telling us something about luck."

Put another way: It could be that Mars is just more static than anticipated - or that InSight landed in an especially quiet period.

Seismologists will have to keep waiting patiently for those larger quakes in order to study layers deep below the crust. "Sometimes you get big flashes of amazing information, but most of the time you're teasing out what nature has to tell you," said InSight Principal Investigator Bruce Banerdt of JPL. "It's more like trying to follow a trail of tricky clues than having the answers presented to us in a nicely wrapped-up package."

The Wind May Hide Quakes

Once InSight started detecting quakes, they became so regular that, at one point, they were happening every day. Then, in late June of this year, the detections essentially stopped. Only five quakes have been detected since then, all of them since September.

Scientists believe Mars' wind is responsible for these seismically blank periods: The planet entered the windiest season of the Martian year around June. The mission knew that winds could affect InSight's sensitive seismometer, which is equipped with a domed wind and heat shield. But the wind still shakes the ground itself and creates literal noise that covers up quakes. This could also have contributed to what seems like the long seismic silence before InSight's first quake, since the spacecraft landed while a regional dust storm was settling down.

"Before landing, we had to guess at how the wind would affect surface vibrations," Banerdt said. "Since we're working with events that are much smaller than what weɽ pay attention to on Earth, we find that we have to pay much closer attention to the wind."

Surface Waves Are Missing

All quakes have two sets of body waves, which are waves that travel through the planet's interior: primary waves (P-waves) and secondary waves (S-waves). They also ripple along the top of the crust as part of a third category, called surface waves.

On Earth, seismologists use surface waves to learn more about the planet's internal structure. Before getting to Mars, InSight's seismologists expected these waves to offer glimpses as deep as 250 miles (about 400 kilometers) below the surface, into a sub-crustal layer called the mantle. But Mars continues to offer mysteries: Despite hundreds of quakes, none has included surface waves.

"It's not totally unheard of to have quakes without surface waves, but it has been a surprise," Panning said. "For instance, you can't see surface waves on the Moon. But that's because the Moon has far more scattering than Mars."

The dry lunar crust is more fractured than Earth and Mars, causing seismic waves to bounce around in a more diffuse pattern that can last for over an hour. The lack of surface waves on Mars may be linked to extensive fracturing in the top 6 miles (10 kilometers) below InSight. It could also mean that the quakes InSight detected are coming from deep within the planet, since those wouldn't produce strong surface waves.

Of course, untangling such mysteries is what science is all about, and there's more to come with InSight.

JPL manages InSight for NASA's Science Mission Directorate. InSight is part of NASA's Discovery Program, managed by the agency's Marshall Space Flight Center in Huntsville, Alabama. Lockheed Martin Space in Denver built the InSight spacecraft, including its cruise stage and lander, and supports spacecraft operations for the mission.

A number of European partners, including France's Centre National d'Études Spatiales (CNES) and the German Aerospace Center (DLR), are supporting the InSight mission. CNES provided the Seismic Experiment for Interior Structure (SEIS) instrument to NASA, with the principal investigator at IPGP (Institut de Physique du Globe de Paris). Significant contributions for SEIS came from IPGP the Max Planck Institute for Solar System Research (MPS) in Germany the Swiss Federal Institute of Technology (ETH Zurich) in Switzerland Imperial College London and Oxford University in the United Kingdom and JPL. DLR provided the Heat Flow and Physical Properties Package (HP3) instrument, with significant contributions from the Space Research Center (CBK) of the Polish Academy of Sciences and Astronika in Poland. Spain's Centro de Astrobiología (CAB) supplied the temperature and wind sensors.

## The moons of Mars

The two moons of Mars, Phobos and Deimos, were discovered by American astronomer Asaph Hall over the course of a week in 1877. Hall had almost given up his search for a moon of Mars, but his wife, Angelina, urged him on. He discovered Deimos the next night, and Phobos six days after that. He named the moons after the sons of the Greek war god Ares — Phobos means "fear," while Deimos means "rout."

Both Phobos and Deimos are apparently made of carbon-rich rock mixed with ice and are covered in dust and loose rocks. They are tiny next to Earth's moon, and are irregularly shaped, since they lack enough gravity to pull themselves into a more circular form. The widest Phobos gets is about 17 miles (27 km), and the widest Deimos gets is roughly 9 miles (15 km).

Both moons are pockmarked with craters from meteor impacts. The surface of Phobos also possesses an intricate pattern of grooves, which may be cracks that formed after the impact created the moon's largest crater — a hole about 6 miles (10 km) wide, or nearly half the width of Phobos. They always show the same face to Mars, just as our moon does to Earth.

It remains uncertain how Phobos and Deimos were born. They may have been asteroids captured by Mars' gravitational pull, or they may have been formed in orbit around Mars the same time the planet came into existence. Ultraviolet light reflected from Phobos provides strong evidence that the moon is a captured asteroid ,according to astronomers at the University of Padova in Italy.

Phobos is gradually spiraling toward Mars, drawing about 6 feet (1.8 meters) closer to the Red Planet each century. Within 50 million years, Phobos will either smash into Mars or break up and form a ring of debris around the planet.

## What created this enormous spiral in the Martian north pole? Wind. And Time.

In some ways, the north pole of Mars is like Earth's. Brutally cold, covered in water ice, yet chillingly beautiful. A big difference is that Earth's arctic area is ocean, while that of Mars is built up on solid ground.

Another big difference is that the Martian north polar cap has an enormous spiral-shaped trough system in it, covering an area of a million square kilometers — 50% bigger than Texas.

The Martian north polar ice cap has a spiral trough pattern in it, possibly due to erosion. This mosaic is created from a series of images from Mars Express, taken in summer so the seasonal carbon dioxide ice doesn’t block the troughs. Credit: ESA/DLR/FU Berlin/J. Cowart, CC BY-SA 3.0 IGO

It's absolutely spectacular, one of the largest geologic megastructures in the solar system. The question is, how did this trough system form?

This is very cool and how it works is a bit subtle.

They found that the troughs are not continuous, like the spiral arms of a hurricane. Instead, each arm is actually a series of small rectangular troughs laid out end-to-end, like sausage links, which they call cells. High-resolution images of the cells shows not just a lack of ice but also layering in the walls, indicative of erosion.

Detail from near the north pole of Mars in local summer 2006 winds pick up dust from exposed areas and blow it over the ice. Credit: ESA/DLR/FU Berlin, CC BY-SA 3.0 IGO

The layers are from the rock underneath the ice, part of a huge plain over the north pole called Planum Boreum (literally “northern plain”). The rock is covered in a thick sheet of permanently frozen water ice on average a couple of kilometers thick. In the winter carbon dioxide freezes out of the air on Mars and forms a dry ice deposit a meter or so thick on top. This hides the troughs in images, but ones taken in northern summer show them clearly.

Katabatic winds blow through the ice cap: Cold, denser air at higher elevations that flows down to lower elevations. The cap is higher in the center than at the edges farther south, so the wind flows south.

Except it doesn't. It would, but Mars spins. It rotates once every 24.5 hours or so, and this creates a Coriolis force which causes the wind to veer west. I explained this in an article about how this creates a hurricane's spin on Earth — read that for details.

Think of it this way: If you stood on the north pole you'd simply spin in place once per day. But if you go farther south you go in a circle around the pole, and the circle gets bigger the farther south you go. Wind flowing down from the north moves south, but the land under it moves faster to the east, leaving it behind. If you were standing on that land, you'd feel a wind blowing to the southwest. The end result is that a stream of air will bend to the west, farther west the farther south you go.

An oblique view of the Martian north polar cap using images from Mars Express combined with laser altimeter data to artificially change the perspective. The spiral trough pattern is obvious. Credit: ESA/DLR/FU Berlin, NASA MGS MOLA Science Team

The scientists hypothesize that if that wind hits a small pit in the ice it will erode it, making it bigger and deeper. When it hits the downwind wall of the pit the air will naturally be pushed to the sides. Over time this elongates the pit, creating a roughly rectangular depression or trough in the ice perpendicular to the wind direction. The wind always seems to flow to the southwest due to the Coriolis force, so these small troughs will naturally align themselves in a clockwise spiral going around the pole.

There are some complicated details to this, but that's the overall picture. There is an older idea that katabatic winds flow down the spiral arms, but this new idea has it flowing across them, and that's why they form in the first place.

They measured the amount of ice eroded away, and it's staggering: 40,000 cubic kilometers! That's ten times the volume of the Grand Canyon. It's a lot of ice. Where did it go?

An impact on Mars excavated a crater dozens of meters wide. Ice can clearly be seen, meaning there’s a layer of ice under the Martian surface even as far as south 44° N. Credit: NASA/JPL-Caltech/Univ. of Arizona

They think it wound up in the mid-latitude regions of Mars to the south. A layer of water ice exists under the dust and sand dunes there, discovered when small, young impact craters were seen from orbit: The impacting asteroids carved out chunks of the surface, revealing fresh water ice just below the surface.

When did this spiral pattern form? It's not clear, but looking at crater counts, climate variations on Mars, and the erosion in the ice versus known depositional ages, they find the troughs may have formed as long as a few million years ago, but might also be incredibly young: Just 50,000 or so years old.

So, not only do they form one of the largest megastructures in the solar system, it's also one of the youngest. How young, though, isn't clear.

Mind you this is a hypothesis, and not proven, but it does seem — if you will — to hold water. Frozen water, but still. It'll be interesting to see if other planetary scientists can in time support or refute it.

And this is another way Mars is like Earth: It's still changing, all the time.

## Causes:

Mars has no protective magnetosphere, as Earth does. Scientists believe that at one time, Mars also experienced convection currents in its core, creating a dynamo effect that powered a planetary magnetic field. However, roughly 4.2 billions year ago – either due to a massive impact from a large object, or rapid cooling in its core – this dynamo effect ceased.

Artist’s rendering of a solar storm hitting Mars and stripping ions from the planet’s upper atmosphere. Credits: NASA/GSFC

As a result, over the course of the next 500 million years, Mars atmosphere was slowly stripped away by solar wind. Between the loss of its magnetic field and its atmosphere, the surface of Mars is exposed to much higher levels of radiation than Earth. And in addition to regular exposure to cosmic rays and solar wind, it receives occasional lethal blasts that occur with strong solar flares.

## 10 Need-to-Know Things About Mars

### Small Planet

If the Sun were as tall as a typical front door, Earth would be the size of a dime, and Mars would be about as big as an aspirin tablet.

### Fourth Rock

Mars orbits our Sun, a star. Mars is the fourth planet from the Sun at an average distance of about 228 million km (142 million miles) or 1.52 AU.

### Longer Days

One day on Mars takes a little over 24 hours. Mars makes a complete orbit around the Sun (a year in Martian time) in 687 Earth days.

### Rugged Terrain

Mars is a rocky planet. Its solid surface has been altered by volcanoes, impacts, winds, crustal movement and chemical reactions.

### Bring a Spacesuit

Mars has a thin atmosphere made up mostly of carbon dioxide (CO 2 ), argon (Ar), nitrogen (N 2 ), and a small amount of oxygen and water vapor.

### Two Moons

Mars has two moons named Phobos and Deimos.

### Ringless

There are no rings around Mars.

### Many Missions

Several missions have visited this planet, from flybys and orbiters to rovers on the surface.The first true Mars mission success was the Mariner 4 flyby in 1965.

### Tough Place for Life

At this time, Mars' surface cannot support life as we know it. Current missions are determining Mars' past and future potential for life.

### Rusty Planet

Mars is known as the Red Planet because iron minerals in the Martian soil oxidize, or rust, causing the soil and atmosphere to look red.

## Why is everyone so obsessed with going to Mars? Here are some other worlds ripe for exploration

Credit: NASA/JPL-Caltech/Space Science Institute

Last month, China successfully landed and deployed the Zhurong rover on Mars, becoming the second country ever to set wheels on the surface of the red planet.

Last year the United States, the United Arab Emirates and China all launched missions to Mars, taking advantage of the relatively short journey time offered by the two planets' unusually close proximity.

Why are planetary scientists so obsessed with Mars? Why spend so much time and money on this one planet when there are at least seven others in our solar system, more than 200 moons, countless asteroids, and much more besides?

Fortunately, we are going to other worlds, and there are lots of missions to very exciting places in our solar system—worlds bursting with exotic features such as ice volcanoes, rings of icy debris, and huge magnetic fields.

There are currently 26 active spacecraft dotted around our solar system. Some are orbiting other planets and moons, some have landed on the surfaces of other worlds, and some have performed fly-bys to beam back images. Only half of them are visiting Mars.

Included in those 26 spacecraft are long-term missions like Voyager 1 and 2—which are still operational after over 40 years and have now left the Solar system and ventured into interstellar space. And it also includes some less famous, but no less weird and wonderful, spacecraft.

Take the Juno spacecraft in orbit around Jupiter, for example. Launched in 2011, it arrived in orbit around Jupiter almost five years later. It is now measuring various properties of the giant planet, including its magnetic field, atmospheric conditions, and determining how much water is in Jupiter's atmosphere. This will help theorists work out which planet formation theory is correct (or if new theories are needed). Juno has already surpassed its planned seven-year mission duration, and has been extended to at least 2025.

Active space probes in the Solar System. Credit: Olaf Frohn - http://www.planetary.org/multimedia/space-images/charts/whats-up-in-the-solar-system-frohn.html (image link), CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=80963751

One of the most complex feats of astrodynamics was completed late last year when the Japanese Space Agency (JAXA) not only landed a spacecraft on an asteroid, but in a spectacular slingshot maneuver, returned a sample to Earth.

Hayabusa2, named after the Japanese term for a peregrine falcon, completed a rendezvous with asteroid 162173 Ryugu in 2018, surveying the surface and taking samples.

Departing in 2019, Hayabusa2 used its ion engines to change orbit and return to Earth. On December 5, 2020, a sample-return capsule about the size of a hatbox and weighing 16 kilograms was dropped through Earth's atmosphere, landing unscathed at the Woomera Test Range in Australia.

As JAXA begins analyzing the rocks and dust collected on the Ryugu asteroid, Hayabusa2 is off on its travels once more—this time to meet up with a second asteroid, 1998 KY_(26), some time in 2031.

‘Lagrange Points’ are positions in space where the gravitational forces of a two body system like the Sun and the Earth produce enhanced regions of attraction and repulsion. These can be used by spacecraft to reduce fuel consumption needed to remain in position. Credit: NASA/WMAP Science Team

Not included in the list of planetary missions earlier, are those spacecraft trapped in "gravitational wells" within our Solar system.

There are special locations in orbits called "Lagrangian points", which are gravitationally balanced spots between two bodies.

The Solar and Heliospheric Observatory (SOHO) is one of four spacecraft close to the Lagrangian point between the Earth and the Sun, roughly 1.5 million kilometers from Earth (about four times further away than the Moon).

It makes observations of the Sun's outer layer and the solar wind, sending early warning back to Earth of potentially disastrous space weather. Geomagnetic storms from the Sun are powerful enough to hit the Earth with electromagnetic blasts so strong they have been known to take out country-wide power grids.

Another hostile location is our nearest planetary neighbor, Venus. Despite the searing temperatures and crushing pressures on the surface, NASA recently approved funding for two big missions to explore the origins of Venus and its atmosphere. The discovery of phosphine gas in the upper atmosphere led life scientists to believe life may exist at the more habitable and cooler temperatures of higher altitudes.

Hot on the heels of the successful flight of the Ingenuity helicopter on Mars—the first flight of any powered aircraft on another world—NASA's Dragonfly mission will fly a drone through the atmosphere of Saturn's icy moon, Titan. Launching in 2026 and arriving in 2034, the rotorcraft will fly to dozens of promising locations on Titan looking for any chemical precursors or life similar to those on Earth.

So how much does all this cost?

Governments tend to allocate relatively small amounts of their budgets to science and space exploration. Countries typically spend less than 1% of their budget on space missions—far less than social services or military defense.

Deciding what space missions will receive that money is very often driven by public interest. But trying to decide definitively which probe or spacecraft offers the most bang for buck is almost impossible.

When humans first set foot on the Moon, 25% of the world's population watched the video with bated breath, inspiring several generations of space explorers for decades afterwards. You can't put a price on that.