There could be snow on Mars. Here’s how

Evidence found at Hale Crater suggests the presence of liquid water on Mars. Image: Getty/NASA.

Given that there are ambitious plans to colonise Mars in the near future, it is surprising how much we still have to learn about what it would be like to actually live on the planet.

Take the weather, for instance. We know there are wild fluctuations in Mars’s climate – and that it is very windy and at times cloudy (though too cold and dry for rainfall). But does it snow? Might settlers on Mars be able to see the red planet turn white? A new study surprisingly suggests so.

Mars is clearly cold enough for snow. It has ice – the amount of which has varied significantly over time. When its axis is tilted at only a small angle relative to its orbit, its surface is ice-free except for the polar caps. This is the situation today, when its axial tilt is 25⁰ (similar to Earth’s 23⁰ axial tilt).

However, possibly because Mars lacks a large moon to stabilise its spin, there have been times when its spin axis was tipped over by up to 60⁰ – allowing the polar ice caps to spread, maybe even to the extent that there was abundant ice near the equator.

NASA’s Phoenix Mars Lander didn’t see snow on the ground. Image: NASA/JPL-Caltech/University of Arizona/Texas A&M University.

Mars emerged from its most recent ice age about 400,000 years ago. Since then, its polar caps have been small, and any ice surviving near the equator has been buried under dust.

The planet’s atmosphere is of low pressure and very dry. Although it is still possible for clouds to form at an altitude of several kilometres, until now it has been generally believed that any true snowfall would not reach the ground. The clouds, resembling Earth’s cirrus clouds, are believed to form when the small amount of water vapour in the atmosphere condenses (directly from vapour to ice) onto grains of dust lofted skywards during storms.

Shots by the Curiosity rover of cirrus clouds (made of tiny crystals of water-ice) on Mars.

Winter wonderland?

Being only a few micrometres in size, ice particles falling from the clouds would would drop at about only a centimetre a second. This allows more than enough time for them to evaporate before reaching the ground (strictly speaking, the process should be called “sublimation”, because the ice goes directly to vapour, without melting first). Overnight and seasonal frost spotted on Mars have been explained by water-ice particles falling quickly because they had been made temporarily larger and heavier by an outer coating of frozen carbon dioxide from the atmosphere.

Seasonal frost (or snowfall?) in gullies on a crater wall on Mars, at 60⁰ N. This view is about 800 metres wide. Image: NASA/JPL/University of Arizona.

The new study, published in Nature Geoscience, has found a way in which tiny specks of water-ice could travel down to the ground without this strange frozen carbon dioxide coat. If correct, this would mean genuine snow on Mars – just like that on Earth. The team used measurements from two orbiting spacecraft (the Mars Global Surveyor and Mars Reconnaissance Orbiter) to study how temperature varies with height in the martian atmosphere. They found that at night, the lower atmosphere below ice clouds can become unstable, because it becomes less dense below than above.

This leads to rapid downdrafts of air, travelling at about 10 metres per second, which could carry ice crystals to the surface too quickly for them to “evaporate”. However, the snow layer would probably be thin and not last too long before it sublimes back into the atmosphere – where it could form new clouds and snowfall.

The phenomenon is similar to what is known on Earth a “microburst”, when a localised 60mph (97km per hour) downdraft below a thunderstorm can be powerful enough to flatten trees. The same process can also be responsible for intense snowfall at a particular location, by carrying snowflakes groundward in a blast, punching through the near-surface layer of air that would normally be warm enough to melt them.

A microburst on Earth.

Snow has not yet been observed in the process of actually reaching the ground on Mars, but it has been seen falling through the sky. NASA’s Phoenix lander, which landed at 68⁰ N in 2008 and became famous for finding ice below the surface when it scraped the dirt away, studied the sky above too. It used a LIDAR (like radar but relying on reflections from a laser beam) to probe the atmosphere, and on at least two nights observed curtains of falling snow hanging below the cloud layer.

Frost or a light dusting of snow seen at the Viking 2 lander site, Utopia Planitia, Mars. Image: Vandencbulek Eric/creative commons.

The ConversationIf a downdraft powerful enough had occurred, then maybe one morning Phoenix would have woken up to a winter wonderland, instead of the usual red landscape – at least for a few hours.

David Rothery is professor of planetary geosciences at The Open University.

This article was originally published on The Conversation. Read the original article.


 

 
 
 
 

You’ve heard of trainspotters and planespotters. Now meet Britain’s growing army of busspotters

Some busspotters in action. Image: Damian Potter.

In the summer of 2014, with too much time on my hands and too little to do, I found myself in the middle of an incredibly active, 200+ person Facebook group. How I ended up here (record scratch, freeze frame) is a little too convoluted and stupid to explain – but what I found was a world that I a) could not have imagined nor b) had any clue even existed.

The group I tumbled into was what I now understand to be a very, very small example of a “busspotting” group – that is, a Facebook group full of dedicated bus enthusiasts which exists to share pictures of buses they see on the road. This group had members from all over the country, with a concentration on northern buses, and was predominantly filled with young, white men.

What I expected to see was a range over relatively interesting buses, holding some significance or another, that were tough to find in your average day-to-day life. This was, largely, not the case. What fascinated me was that the vast majority of the group was not focused on unique buses, new buses, historically significant buses, and so on – but simply on the average bus and or bus route you might take just to get around your city.

What was even more bizarre to me was that people from across the country were meeting up in small towns (Morpeth, Livingston, Stevenage) to take seemingly mundane bus rides to other equally small places (Washington, Gloucester, Grimsby). The busspotters would travel hours on end to meet at these locations simply to ride this bus, often for three or four hours, and experience a bus route they’d never been on before or one that they just particularly enjoyed.

Ooooh. Image: Damian Potter.

After a couple of weeks of silently watching and one semi-ironic post, I left the group. And, for the next three years, I gave barely a thought to bus enthusiasm, as no busspotter group/page/person crossed my path. Unlike similar enthusiasms like planespotting and trainspotting, it didn’t seem to me that busspotting had any significant following.

But, as is the way of these things, a weird thread on Twitter three summers later sparked my memory of my short time in this group. I wanted to see what busspotting was actually and about and if, in fact, it was still a thing.

So I spoke to Damian Potter, an admin on several popular busspotting groups, about what it’s like to be deep into the busspotting scene.

“I used to sit upstairs on double decker buses and 'drive' them, including the pedal movements!” Damian announced right off the bat, speaking of his childhood. “I've been driving coaches at home and abroad since I passed my PCV test in 1994. I've been driving for Transdev Harrogate and District Travel since 1998.”

Damian, as you might have gathered, has been a busspotter since his early youth. Now, at the age of 50, he manages four different busspotting Facebook groupsm, mostly based around the Harrogate area (Transdev Enthusiasts, The Harrogate Bus Company, iTransport Worldwide and Spotting Bus and Coach Spotters). Some of them have over a thousand members.

He also participates in busspotting IRL, travelling around the country participating in busspotting meet-ups and events and co-organising trips along different bus routes. When I asked him what busspotting was to him, he explained that it can manifest in different ways: some people focus on makes of bus and routes, other focus on particular bus companies (National Express is particularly popular). Of course, bus enthusiasm is not solely a British phenomenon, but busspotters can certainly be found in practically every corner of the UK.

“People tend to think that spotters hang around bus stations furtively, with a camera and some curly cheese sandwiches, but this isn't really the case,” Damian continued. That said, he also mentioned some particularly hardcore bus nuts who have been known to trespass on company premises to be the first to snap a picture of a new bus.

“They really do produce some brilliant pictures, though,” he added.


Although much of busspotting culture happens online, predominantly on Facebook, groups often have what are called ‘running days’ which involve meet ups having to do with particular routes. Damian mentioned one particularly popular day following the London Routemaster buses that happen periodically. Not only do these routes draw in enthusiasts, he noted, but also draw huge numbers of tourists who want to claim they’ve ridden on the original London buses.

“I reckon the general public miss the old Routemaster buses. There is only one 'heritage' route in London which still uses Routemaster buses and that's the 15 service between Trafalgar Square and Tower Hill.”

Despite this widespread interest in buses and bus history, though, busspotters often find themselves treated as the lesser of the motor enthusiasts. This became clear to me almost immediately when speaking to Damian, and continued to strike me throughout our conversation; without my saying anything sarcastic, malicious, or snarky, he became instantly defensive of his fellow enthusiasts and of his hobby.

When I asked him why he felt this immediate need to defend busspotting, he explained that people often ridicule busspotters and bus enthusiasm generally, arguing that bus drivers are the most common attackers. “However,” he noted, “if I bring a load of pictures into the canteen they're the first to crowd around to see bus pictures...”

Aaah. Image: Damian Potter.

Despite being perceived as an often-mocked hobby, bus enthusiasm is expanding rapidly, Damien claims. “The bus enthusiast culture is growing, with younger generations getting more involved.” Drawing in new, younger enthusiasts has become easier thanks to social media, as has creating real personal connections. Social media has made it easier for bus enthusiasm to not just stay afloat, but actually thrive over the last several years.

It’s so widespread, in fact, that a national competition is held every year in Blackpool to mark Bus Driver of the Year (Damian himself came in 34th out of 155 back in 2002). This event draws in everyone from the bus world – drivers, manufacturers, tour companies, and enthusiasts alike. Here is one of the many places where great friendships are forged and busspotters who’ve only known each other online can finally meet face-to-face. “Personally I have made some great friends through Facebook,” Damian told me. “I have even stayed over at a friend's house in London a couple of times.”

Busspotting may be less well-known than motor enthusiasms like planespotting and trainspotting, but that very well could change. Thanks to active social media groups and regular in-person meet-ups, people have been able to use busspotting forums as not only a way to find lifelong friends, but also spend more of their free time exploring their hobby with the people they’ve met through these groups and pages who share their enthusiasm. For all the flack it may receive, the future of busspotting looks bright.

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