How to find a meteorite that’s fallen to Earth


Phil Bland, Curtin University

A bright fireball lit up the night sky around Kati Thanda (Lake Eyre South) in South Australia on November 27, 2015.

But how to find the impact site of that meteorite? And how can we know where in the solar system the object came from?

Thankfully, a new meteorite tracking system we’ve installed in Australia has enabled us to answer these questions, helping us better understand the history and composition of our solar system.

Meteorites are the oldest rocks in existence. They contain a unique physical record of the formation and evolution of the solar system, and the processes that led to terrestrial planets.

They sample hundreds of different heavenly bodies, a compositional diversity that spans the entire inner solar system.

But the most basic piece of data – context – is absent. In almost all cases, meteorite researchers have no idea where their samples came from.

What they need are orbits and the ability to track meteorites back to their place of origin in the solar system. The goal of the Desert Fireball Network is to provide that data.

A network of ‘eyes’

This is a project that started in 2012 and since then we’ve installed a network of 32 automated observatories in remote areas of Australia. They are capable of operating for 12 months without maintenance, storing all imagery collected over that period.

The locations of some of the automated camera stations.
Desert Fireball Network (clickable map available), Author provided

Although they are high resolution intelligent imaging systems, they cost around A$5,000 each, which is only a fraction of the cost of previous systems. We’ve completely automated data reduction, so we can potentially scale up the system to arbitrary size without needing hordes of poor PhD students doing manual labour.

And members of the public can contribute by sending in their own reports via a smartphone app that we’ve developed called Fireballs in the Sky.

Trying to track an object moving at many kilometres a second, from the edge of the Earth’s atmosphere to the surface, isn’t easy. You have to account for everything from minor distortions in the camera lenses, to the effect of winds blowing the object off course when the light has gone out.

We would only know that it worked when we found a rock on the ground.

One of the automated cameras keeping watch on the sky.
Desert Fireball Network, Curtin University, Author provided

A green flash in the sky

When that fireball lit up the skies above South Australia in November, it was imaged by five Desert Fireball Network automatic observatories. The stations sent alerts to our server in Perth, attaching thumbnails of the fireball image.

With data from just a couple of cameras, we could tell pretty quickly that we had a meteorite on the ground. First, we had to get out to South Australia to pick up additional data from cameras that weren’t online, so that we could precisely triangulate the fireball.

We took a light aircraft flight from William Creek, which showed us that there was a feature on the surface that might be where the rock plunged into the mud. Now we had to get out on the lake.

Some of our team set to work pulling together all the data. The more accurately we could pinpoint the fall position, the easier any search would be. Their analysis showed that the object came in at a very steep angle, with a velocity of 50,000km/h, and punched down low in the atmosphere, still visible as a fireball at 18km altitude.

When it entered the atmosphere, it was about 80kg. At the end of the fireball it had more likely been whittled down to between 2kg and 6kg.

Alongside the effort to work all this out, we were putting together logistics for the trip. We knew we had to get there quickly. There had already been rain. Much more of it and any trace of the rock might be wiped away.

In addition, Kati Thanda has spiritual significance for the Arabana people. We would need their permission before we could go out on the lake. But the Arabana understood the urgency, and gave consent almost immediately. The Arabana guides, Dean Stuart and Dave Strangway, who came with us on the trip were a huge help.

The search is on

We got to the lake shore on December 29. But the lake doesn’t have a firm surface; it’s thick mud. We had to pick our way out to the fall site – almost at the centre of the lake – trying to find a route that would support a quad bike. Eventually, we found a way in.

Next day we got to the site, and searched the area, but didn’t find any trace of the feature that we’d seen a couple of weeks before from the air. Time was running out. Rain was coming in. We figured we might have just have one more day left.

Professor Phil Bland and PhD student Robert Howie digging the meteorite out of the mud in the middle of Kati Thanda (Lake Eyre) South.
Jonathan Paxman, Desert Fireball Network, Author provided

So we decided to double down: one of our team would fly over the site, while two of us would search on the ground. If they saw anything from the air they would radio, circle the spot, and we could check it immediately.

It was overcast and drizzling as we headed out to the shore, but heavy rain held off long enough for us to get to the fall site. For an hour, the plane just circled.

Then we got a call that they’d seen it. We ran to the spot, and found the last remnant of the feature that our friend had seen a couple of weeks before. The meteorite had punched a deep hole in the mud.

Digging down through that pipe my fingers eventually touched a rock. We’d found our meteorite. The rock is 1.6kg in weight, a bit lighter than we’d expected, and it’s probably an ordinary chondrite, the most common type of meteorite. But we need to do some analyses to tell for sure.

The 1.6kg meteorite close up.
Desert Fireball Network, Curtin University, Author provided

An unexpected surprise

We didn’t know it when we built the network, but it turns out it can do a lot more than we ever expected. We can track satellites, space debris and rocket launches. We’ve even tested systems that will let us do fundamental astronomy. And, with a minor upgrade, we’ll have a facility that can spot supernovae and optical counterparts to gamma ray bursts.

But it’s the potential for planetary research that still gets us excited. Already, we’ve seen more fireballs than have ever been recorded up to now, giving us a unique window on what’s hitting the Earth.

As we recover more rocks, we will gradually build a geological map of the inner solar system. If we can link a meteorite to an asteroid, then we essentially have a sample-return mission to near-Earth asteroids, without the need for spacecraft.

This first rock we’ve recovered is just the start. In itself, it’s a research gold mine. But it also proves that our system works so there should be many more.

The Conversation

Phil Bland, ARC Laureate Fellow, Curtin University

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

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Mortal poison: the story of how venom works


Ken Winkel, University of Melbourne

Centuries ago it was thought that snakes caused their deadly effects because of “a mortal poison that lurked in the bile”. It wasn’t until the 17th century that Italian doctor Francesco Redi (1626-1697) conclusively located the poison as being in the yellow liquid from glands attached to the two front teeth of venomous snakes.

Shortly afterwards, English physician Richard Mead (1673-1754) went one step further and personally drank, without ill effect, viper venom to show that it must be injected into the body to cause harm.

The study of venom has progressed so that we now have a detailed understanding of what’s in venom and how the constituent toxins work. The major ways that venom can be a “mortal poison” are explained below.

Neurotoxins

Perhaps the most common type of poison in animal venoms is the nerve toxin. This group can acts in diverse ways to block or over-stimulate the nervous system – rarely a good thing.

The most dangerous of these are the ones that block nerve signalling, causing paralysis of the muscles required for breathing. Depending on the toxin, such paralysis may be very rapid (blue-ringed octopus venom can act within minutes) or take many hours (neurotoxins of the taipan snake typically progress over five to ten hours).

Francesco Redi worked out where the poison of venomous snakes is stored.
Public domain via Wikimedia Commons

The blue-ringed octopus shares a common toxin type with the puffer or fugu fish – most famous as Japan’s deadly delicacy. Both contain a very powerful nerve blocker called tetrodotoxin.

Typically, tetrodotoxin poisoning initially causes a tingling around the mouth. If the dose is high enough, this will be followed by progressive difficulty in breathing. And, if untreated, it may be fatal.

Snake venoms, by contrast, start their paralysing effects on the muscles around the eyes (typically manifest as fixed dilated pupils, reduced eye movements and droopy eyelids). If not treated with antivenom, these early signs will eventually be followed by increasing difficulty talking, swallowing and, ultimately, breathing.

The Australian paralysis tick also has neurotoxins but, unlike snakes, these toxins take many days to cause paralysis. It usually starts by causing weakness in the legs.

Many paralysing venoms contain a cocktail of molecules that act together but in different ways to interfere with the transmission of nerve impulses.

The most dangerous paralysing toxins destroy the nerves themselves. Some Australian snake venoms, such as the mainland tiger snake, contain both receptor blocking and nerve destructive types of neurotoxins. Once this latter type of damage occurs, it may take weeks for the nerves to repair and during this time you may not be able to breathe without external support.

Some venomous marine snails have tens of different types of neurotoxins in their venom and can control the mix of toxin types depending on whether they’re protecting themselves from attack or hunting prey.

Impact on blood and heart

Another potentially lethal effect of snakebite, rarely seen with other types of venoms, is altered blood clotting. Most of Australia’s dangerous snakes have toxins in their venom that cause the body to destroy factors that help clot blood.

As well as being extremely painful, a brush with a box jellyfish can kill you in minutes.
Jellyfish image from http://www.shutterstock.com

The eastern brown snake, for example, can cause a very severe clotting disturbance. This type of venom can cause the sudden death of some people bitten by these snakes.

Arguably the most dangerous venom in the world is that of the box jellyfish, Chironex fleckeri, because of its ability to kill a healthy adult human in minutes. This remarkable lethality is attributed to powerful toxins that are injected into the skin through millions of tiny venom-filled harpoon-like weapons on the jellyfish tentacles.

Once in the circulation, these toxins seem to home in on, and punch holes in, the outer membrane of heart muscle cells. These holes disturb the smoothly co-ordinated contraction of the heart muscles.

Unsurprisingly, left untreated, this form of venom toxicity can cause death soon after you’ve been stung.

Muscle destruction and pain

A more insidious effect, particularly of snake venoms, is muscle destruction known as myotoxicity. While not as quick as the effect on blood clotting, heart function or nerve signalling, myotoxicity can also be lethal.

Typically, snake venom toxins dissolve the membrane of muscle cells. Not only is this a painful experience, it also causes the muscle protein, known as myoglobin, to leak into the urine, potentially poisoning the kidneys in the process.

English physician Richard Mead (1673-1754) drank viper venom to show it must be injected into the body to cause harm.
Mezzotint by R. Houston after A. Ramsay via Wikimedia Commons, CC BY-SA

People bitten by tiger snakes occasionally require kidney dialysis because of this. In some Asian countries, such as Myanmar, snakebite is a leading cause of renal failure.

Myotoxicity can also lead to massive increases in blood potassium levels, leached from the injured muscle cells. This effect can itself cause fatal damage to the normal rhythm of the heart.

Although many venoms have evolved to rapidly paralyse and digest prey, another important venom action is defence.

Venomous bees, wasps and ants are well known to most of us because of the characteristic pain that’s produced by their stings. Stinging fish and most venomous jellyfish are also conspicuous by their more prolonged painful stings.

Aside from the physical trauma to the skin from a bite or a sting, these venoms frequently contain toxins that act in various ways to injure cells, trigger inflammation and even kill skin cells. All of this can cause severe pain. The stonefish and box jellyfish are examples of this potent venom effect.

However, least you think the news about venoms is all bad, it is worth recalling the words of Claude Bernard, 19th century father of experimental medical science. Concerning the wide utility of venoms as scientific tools he wrote: “Poisons are veritable reagents of life, extremely delicate instruments which dissect vital units”.

Indeed such “reagents” have aided in many past Nobel Prizes . But that’s another story…

Learn more about the story of venom at the Medical History Museum’s online exhibition.

This article is part of our series Deadly Australia. Stay tuned for more pieces on the topic in the coming days.

The Conversation

Ken Winkel, Toxinologist; Senior Research Fellow, Australian Venom Research Unit, University of Melbourne

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