Megacryometeor Madness
or: How I Learned to Stop Worrying and Watch the Sky
Imagine being caught in a hailstorm for a moment. We’ve almost certainly all had that experience at some point in our lives, where the rain suddenly gives way to tiny or sometimes not so tiny balls of ice that can actually hurt as they bounce off the top of your head. Now imagine that these balls of ice are not so tiny. We’ve all heard of hailstorms where golf ball sized hailstones fell and damaged houses and cars. Fortunately, these hailstorms are reasonably rare and it’s not really worth investing in a solid steel umbrella “just in case”.
Hail forms in thunderstorm clouds, where water droplets get caught in strong updraughts of air within the cloud. As the droplet rises, it enters regions where the temperature drops below freezing and become supercooled. They freeze and begin to drop, before getting raised up again by the updraught, collecting more moisture and refreezing. Hailstones typically display an onion like structure, with thick, translucent layers, alternating with layers that are thin and opaque. These balls of ice bounce around on the wind inside the cloud for up to half an hour, building up layers and layers, until the weight of it can no longer be supported by the winds and begins to fall. Due to the nature of the freezing process the water goes through, the outer layer can be ‘sticky’, meaning that it can adhere to other hailstones on its travels through the cloud and larger hailstones can be jigsawed together than otherwise would be generated within the cloud. These can reach sizes of up to 15 cm and weigh up to 500 grams in the more extreme circumstances. Definitely not something you want landing on you, your house or car. A thunderstorm that produces hail is known as a hailstorm.
Hail can fall well away from the parent storm however — sometimes up to 4 km away and with considerable speed. The size of the individual hailstone dictates how fast it will fall, with a 1cm hailstone having a terminal velocity of around 20 mph and an 8cm hailstone having a terminal velocity of around 110 mph. The records for hail are equally impressive — the largest recorded had a diameter of 20cm and the heaviest weighed an impressive 1kg.
On rare occasions, a hailstorm can become stationary whilst producing hail and significant depths of hailstones can accumulate. In Boulder County, Colorado in 2010, a depth of 30cm was reported during a particularly bad hailstorm.
However, there exists a rare, mysterious type of hailstone, one not commonly known about and even more rarely seen — the Megacryometeor. These hailstones are typically many times the size and mass of regular hailstones, often fall from clear skies and nobody really knows how they form, except that they share many similarities with their tinier hailstone relatives — onion like layers and are usually made from local atmospheric water.
They were named by Jesús Martínez-Frías, a planetary geologist at the Center for Astrobiology in Madrid in the year 2000 after the city was host to a mysterious fall of them over the course of 10 days from clear, blue skies.
It has been suggested that these gigantic hailstones might have their origins in aircraft, but no evidence has yet been found — most water found on aircraft is either purified (drinking water) or chemically treated (waste water) and the ice that makes up megacryometeors contains neither of these types of water, but instead share more in common with the water that is in the atmosphere in the area. It is possible that they form from condensation on the outer shell of aircraft, yet reports of giant balls of ice falling from the sky predate the invention of powered flight.
It is impossible for these balls of ice to form in storm clouds, as they are simply too massive to be supported by even a massive thunderstorm; and reports of them are usually that they fall alone, out of an almost clear, blue sky. It is simply not yet known what these things are, or how they form seemingly out of an empty sky. They have sometimes been mistaken for actual meteors, as due to their mass, they can leave small impact craters.
Since 2000, there have been 50 recorded megacryometeor falls. The smallest was around half a kilogram, whilst the biggest, which fell in Brazil and partially wrecked a factory, weighed in at an impressive 50 kilograms.
Analysis on recovered megacryometeors show that they form within a range of temperatures from -10°C to -20°C and that they seem to share the onion like layering associated with more traditional hailstones. When the megacryometeors from Spain were analysed, the results suggested that the ice had formed high up in the upper troposphere. Further atmospheric research using data from NASA showed that a thin jet of ozone depression passed through the areas in Spain where the ice falls took place, causing the troposphere to be warmer than normal and the stratosphere to be cooler and more humid than normal, as well as a particularly strong wind shear in the upper atmosphere.
Megacryometeor falls have been recorded since the early 19th century, but the apparent frequency appears to be increasing over the last 50 years. It has been postulated that this may be a symptom of climate change, but there is no strong evidence either way. Documented megacryometeors that have fallen from clear skies include 1829 in Córdoba, Spain, with a 2 kg ball of ice and in 1851 in New Hampshire which recorded a 1kg megacryometeor. More recent cases include a 9 kg fall in Batley, West Yorkshire in 1991, and probably the best documented UK fall of a megacryometeor was on 2nd April, 1973, in Manchester. The block weighed 2 kg and consisted of 51 layers of ice. Its origin was not determined.
If they are the byproduct of ice forming on aircraft, or if they are a genuine natural weather phenomenon, the thought that the frequency of the falls is increasing and the sheer size of these megacryometeors should be enough to cause the occasional glance upwards on a nice sunny day, just to make sure there isn’t a gigantic ball of ice hurtling down to earth near you.
