Nature facts

The Colossus of Rhodes, one of the Seven Ancient Wonders of the World, stood for a mere 50 years before it was destroyed by an earthquake. Its ruins stood and attracted visitors for way longer than the original statue (reportedly hundreds of years) before it was finally recycled for scrap metal.

Until 1993, the BT Tower was an official state secret despite being a 177-metre tall structure in the middle of central London that was open to the public.

A giant American wasp called the tarantula wasp has a sting so painful, one peer-reviewed journal advises anyone who gets stung to "lie down and scream" to avoid further injury.

In 2004, a starquake was detected, which was so powerful that if the star was located within 10 light years of Earth, it would have likely caused a mass extinction.

With each passing year, the effects of rising global temperatures become even more obvious, while the chances of avoiding greater catastrophes in the future retreat like every melting glacier.

Desperate to avoid worst-case scenarios, researchers have proposed various measures that could, at the very least, buy us the time we might need to mature as a society and work to undo the damage.

Blasting a steady stream of dust from the surface of the Moon is the latest suggestion to get a solid scientific appraisal, with University of Utah computational astrophysicist Ben Bromley and computer scientist Sameer Khan and Smithsonian Astrophysical Observatory astrophysicist Scott Kenyon giving the idea a tentative thumbs up.

This isn't to say it falls into the 'good idea' category. Not yet, at least. But as far as extreme measures go, it's a plan that could come with far fewer risks and potentially lower costs than many other strategies being entertained for emergency options.

Thanks to historic levels of carbon dioxide lingering in our atmosphere, every joule of solar radiation that warms the planet has a slightly lower chance of returning to space.

The logical thing to do would be to work together to kick our nasty habit of smoking fossil fuels. Shocking as it seems, it could be faster and easier to engage in mammoth-scaled engineering projects that literally reflect a proportion of sunlight before it hits Earth and is converted into a form that's likely to stick around as heat.

Early suggestions of adding a thin haze made of sulfur dioxide particles to our atmosphere seem practical and economically feasible. However, the environmental consequences might just swap one crisis for another.

Scattering a swarm of tiny parasols or blowing a curtain of fancy bubbles into space could do the trick, with the advantage of being disassembled faster than the IPCC can say, "Golly, that sure was a mistake!"

On the other hand, the sheer amount of energy and effort required to launch and steer a sizable flotilla out to a convenient dead zone between the Sun's gravity and our planet is unprecedented, increasing the risk of failure.

Bromley, Khan, and Kenyon have done the math on the characteristics of a 10-billion-kilogram dust cloud doing much the same job.

The idea itself has been kicked around as a less intrusive version of sulfur being suspended in Earth's atmosphere. It has benefits over more technical space-borne projects, relying on material that doesn't require significant manufacture, doesn't need to be launched from our surface, and doesn't pollute our planet.

Assessing the shadow cast by different kinds of material, the impact of gravitational forces, radiation pressure from sunlight, and the smack of the solar wind, the researchers calculated the qualities and quantities of small rocky fragments required to filter out just under 2 percent of the Sun's rays.

They showed the dust cloud would clear relatively quickly, depending on their size. Micron-sized grains would be pushed out of position within a week, requiring fairly regular top-ups. On the plus side, there'd be no need for adjustments to orbits should things go wrong. Just wait a few days for the fog to lift, and it's business as usual.

According to the researcher's calculations, some orbits could allow dust grains to be mined and shot from the Moon to provide the necessary shade for days on end.

Initial suggestions for a cosmic dust screen temporarily cooling our planet involved the use of asteroids, but why go hunting for distant sources of space dirt when there's a great big ball of it right in our backyard?

Squirting a carefully calculated stream of Moondust from a future lunar station at the right point between the Sun and Earth might be the most cost-effective, risk-free means of keeping our cool until we come to our senses and cut emissions.

Whether such projects ever need to be put on the table and considered seriously will depend on what we learn in the coming decades.

By the end of the century, rising sea levels, heat waves, collapsing ocean currents, and extreme weather events could well make us beg for an artificial volcano of Moondust to save our skins.

A space rock recovered within just a few short hours of entering Earth's atmosphere has revealed there may not be such a thing as a "pristine" meteorite.

The Winchcombe meteorite fell to Earth in February 2021 after exploding mid-air over Gloucestershire in England, and in the days that followed, multiple fragments were retrieved from the surrounding fields and properties, the first in a driveway just 12 hours after the fireball was seen.

Still, that short amount of time was enough for changes to occur in the rock's chemistry. An analysis showed significant and extensive contamination from the terrestrial atmosphere and ground, with salts and minerals that had to have developed within the sample after its arrival at our home planet.

Specifically, researchers found halite, and calcite and calcium sulfate minerals, that formed after the meteorite broke apart in Earth's atmosphere. This contamination is something that scientists will need to take into consideration when studying meteorite fragments in the future.

On the other hand, the findings could also help efforts to protect newly fallen meteorites against terrestrial alteration, as well as geological samples brought home from space – like the samples of asteroid Ryugu delivered to Earth in 2020, or the planned delivery of samples from the surface of Mars.

"The Winchcombe meteorite is often described as a 'pristine' example of a CM chondrite meteorite, and it's already yielded remarkable insights," says Earth scientist Laura Jenkins of the University of Glasgow in Scotland.

"However, what we've shown with this study is that there's really no such thing as a pristine meteorite – terrestrial alteration begins the moment it encounters Earth's atmosphere, and we can see it in these samples which we analyzed just a couple of months after the meteorite landed."

Analysis revealed Winchcombe, as the 4.6-billion-year-old rock is known, to be a rare type of meteorite known as carbonaceous chondrite, made up primarily of carbon and silicon. There's a lot we can learn from such an ancient piece of space rock, but only if we are correctly interpreting what we are looking at.

Jenkins and her colleagues conducted scanning electron microscopy, Raman spectroscopy, and transmission electron microscopy on several samples. These samples included one from the initial driveway find, and several from sheep fields, where they had lain for several days before recovery.

When an asteroid enters Earth's atmosphere, it doesn't just fall down. As it falls, the air in front of it is compressed and heats up, causing the exterior of the meteor to melt and be cast off. Then the next layer melts and sloughs, until it slows down enough that the air is no longer hot enough to melt the rock, leaving the last layer to cool and harden as a thin crust.

A sample of the sheep field meteorite, showing terrestrial alteration. (University of Glasgow)
This is known as a fusion crust, and is the main diagnostic feature to visually determine the difference between a meteorite and just a plain old Earth rock.

Jenkins and her team conducted a thorough study, and found calcite and calcium sulfates – gypsum, bassanite, and anhydrite – had formed on the fusion crust of the meteorite samples found in the sheep field. As this piece of meteorite had lain there for six days, they concluded that the minerals had likely precipitated from the damp environment.

On the driveway sample, they found halite, but only on a section of the sample that was polished after retrieval, in areas relatively rich in sodium. This, they found, was likely due to an interaction between the rock and the humid laboratory environment in which it had been stored for several months.

This finding, the researchers said, suggests that meteorites should be carefully stored in inert conditions, to try to minimize terrestrial contamination.

"It shows just how reactive meteorites are to our atmosphere, and how careful we need to be about ensuring that we take this kind of terrestrial alteration into account when we analyze meteorites," Jenkins explains.

"Understanding which phases are extra-terrestrial and which are terrestrial in meteorites like Winchcombe will not only help our understanding of their formation but will also aid in relating meteorites that have landed on Earth to samples returned by sample return missions. A more complete picture of the asteroids in our Solar System and their role in Earth's development can be built."

Our Solar System is a pretty busy place. There are millions of objects moving around – everything from planets, to moons, to comets, and asteroids. And each year we're discovering more and more objects (usually small asteroids or speedy comets) that call the Solar System home.

Astronomers had found all eight of the main planets by 1846. But that doesn't stop us from looking for more. In the past 100 years, we've found smaller distant bodies we call dwarf planets, which is what we now classify Pluto as.

The discovery of some of these dwarf planets has given us reason to believe something else might be lurking in the outskirts of the Solar System.

Could there be a ninth planet?
There's a good reason astronomers spend many hundreds of hours trying to locate a ninth planet, aka " Planet Nine" or "Planet X". And that's because the Solar System as we know it doesn't really make sense without it.

Every object in our Solar System orbits around the Sun. Some move fast and some slow, but all move abiding by the laws of gravity. Everything with mass has gravity, including you and me. The heavier something is, the more gravity it has.

A planet's gravity is so large it impacts how things move around it. That's what we call its "gravitational pull". Earth's gravitational pull is what keeps everything on the ground.

Also, our Sun has the largest gravitational pull of any object in the Solar System, and this is basically why the planets orbit around it.

It's through our understanding of gravitational pull that we get our biggest clue for a possible Planet Nine.

Unexpected behaviors
When we look at really distant objects, such as dwarf planets beyond Pluto, we find their orbits are a little unexpected. They move on very large elliptical (oval-shaped) orbits, are grouped together, and exist on an incline compared to the rest of the Solar System.

When astronomers use a computer to model what gravitational forces are needed for these objects to move like this, they find that a planet at least ten times the mass of Earth would have been required to cause this.

It is super-exciting stuff! But then the question is: where is this planet?

The problem we have now is trying to confirm if these predictions and models are correct. The only way to do that is to find Planet Nine, which is definitely easier said than done.

The hunt continues
Scientists all over the world have been on the hunt for visible evidence of Planet Nine for many years now.

Based on the computer models, we think Planet Nine is at least 20 times farther away from the Sun than Neptune. We try to detect it by looking for sunlight it can reflect – just like how the Moon shines from reflected sunlight at night.

However, because Planet Nine sits so far away from the Sun, we expect it to be very faint and difficult to spot for even the best telescopes on Earth. Also, we can't just look for it at any time of the year.

We only have small windows of nights where the conditions must be just right. Specifically, we have to wait for a night with no Moon, and on which the location we're observing from is facing the right part of the sky.

But don't give up hope just yet. In the next decade, new telescopes will be built and new surveys of the sky will begin. They might just give us the opportunity to prove or disprove whether Planet Nine exists.