What caused the fireballs that lit up the sky over Australia?



One of the fireballs (highlighted by the red circle) captured over the Northern Territory.
NT Emergency Services

Jonti Horner, University of Southern Queensland

Over the past few days a pair of spectacular fireballs have graced Australia’s skies.

The first, in the early hours of Monday, May 20, flashed across the Northern Territory, and was seen from both Tennant Creek and Alice Springs, more than 500km apart.

The second came two days later, streaking over South Australia and Victoria.

Such fireballs are not rare events, and serve as yet another reminder that Earth sits in a celestial shooting gallery. In addition to their spectacle, they hold the key to understanding the Solar system’s formation and history.

Crash, bang, boom!

On any clear night, if you gaze skyward long enough, you will see meteors. These flashes of light are the result of objects impacting on our planet’s atmosphere.




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Specks of debris vaporise harmlessly in the atmosphere, 80-100km above our heads, all the time – about 100 tons of the stuff per day.

The larger the object, the more spectacular the flash. Where your typical meteor is caused by an object the size of a grain of dust (or, for a particularly bright one, a grain of rice), fireballs like those seen this week are caused by much larger bodies – the size of a grapefruit, a melon or even a car.

Such impacts are rarer than their tiny siblings because there are many more small objects in the Solar system than larger bodies.

Moving to still larger objects, you get truly spectacular but rare events like the incredible Chelyabinsk fireball in February 2013.

That was probably the largest impact on Earth for 100 years, and caused plenty of damage and injuries. It was the result of the explosion of an object 10,000 tonnes in mass, around 20 metres in diameter.

On longer timescales, the largest impacts are truly enormous. Some 66 million years ago, a comet or asteroid around 10km in diameter ploughed into what is now the Yucatan Peninsula, Mexico. The result? A crater some 200km across, and a mass extinction that included the dinosaurs.

Even that is not the largest impact Earth has experienced. Back in our planet’s youth, it was victim to a truly cataclysmic event, when it collided with an object the size of Mars.

When the dust and debris cleared, our once solitary planet was accompanied by the Moon.

The story behind the formation of the Moon.

Impacts that could threaten life on Earth are, thankfully, very rare. While scientists are actively searching to make sure no extinction-level impacts are coming in the near future, it really isn’t something we should lose too much sleep about.

Smaller impacts, like those seen earlier this week, come far more frequently – indeed, footage of another fireball was reported earlier this month over Illinois in the United States.

In other words, it is not that unusual to have two bright fireballs in the space of a couple of days over a country as vast as Australia.

Pristine relics of planet formation

These bright fireballs can be an incredible boon to our understanding of the formation and evolution of the Solar system. When an object is large enough, it is possible for fragments (or the whole thing) to penetrate the atmosphere intact, delivering a new meteorite to our planet’s surface.

Meteorites are incredibly valuable to scientists. They are celestial time capsules – relatively pristine fragments of asteroids and comets that formed when the Solar system was young.

Most meteorites we find have lain on Earth for long periods of time before their discovery. These are termed “finds” and while still valuable, are often degraded and weathered, chemically altered by our planet’s wet, warm environment.

By contrast, “falls” (meteorites whose fall has been observed and that are recovered within hours or days of the event) are far more precious. When we study their composition, we can be confident we are studying something ancient and pristine, rather than worrying that we’re seeing the effect of Earth’s influence.

Tracking the fireballs

For this reason, the Australian Desert Fireball Network has set up an enormous network of cameras across our vast continent. These cameras are designed to scour the skies, all night, every night, watching for fireballs like those seen earlier this week.

If we can observe such a fireball from multiple directions, we can triangulate its path, calculate its motion through the atmosphere, and work out whether it is likely to have dropped a meteorite. Using that data, we can even work out where to look.

A successful meteorite search by the Australian Desert Fireball Network.

In addition to these cameras, the project can make use of any data provided by people who saw the event. For that reason, the Fireballs team developed a free app, Fireballs in the Sky.




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It contains great information about fireballs and meteor showers, and has links to experiments tied into the national curriculum. More importantly, it also allows its users to submit their own fireball reports.

As for this week’s fireball over southern Australia, NASA says it was probably caused by an object the size of a small car. As for finding any remains, they are now likely lost in the waters of the Great Australian Bight.The Conversation

NASA’s record on the location marked in the Great Australian Bight of one of the fireballs over Australia this week.
NASA

Jonti Horner, Professor (Astrophysics), University of Southern Queensland

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Torres Strait Islanders ask UN to hold Australia to account on climate ‘human rights abuses’


Kristen Lyons, The University of Queensland

Climate change threatens Australia in many different ways, and can devastate rural and urban communities alike. For Torres Strait Islanders, it’s a crisis that’s washing away their homes, infrastructure and even cemeteries.

The failure to take action on this crisis has led a group of Torres Strait Islanders to lodge a climate change case with the United Nations Human Rights Committee against the Australian federal government.

It’s the first time the Australian government has been taken to the UN for their failure to take action on climate change. And its the first time people living on a low lying island have taken action against any government.

This case – and other parallel cases – demonstrate that climate change is “fundamentally a human rights issue”, with First Nations most vulnerable to the brunt of a changing climate.

The group of Torres Strait Islanders lodging this appeal argue that the Australian government has failed to take adequate action on climate change. They allege that the re-elected Coalition government has not only steered Australia off track in meeting globally agreed emissions reductions, but has set us on course for climate catastrophe.

In doing so, Torres Strait Islanders argue that the government has failed to uphold human rights obligations and violated their rights to culture, family and life.

This case is a show of defiance in the face of Australia’s years of political inertia and turmoil over climate change.

It is the first time people living on a low-lying island – acutely vulnerable in the face of rising sea levels – have brought action against a government. But it may also be a sign of things to come, as more small island nations face impending climate change threats.

Breaching multiple human rights obligations

Driving this case is an alliance of eight Torres Strait Islanders, represented by the Torres Strait land and sea council, Gur A Baradharaw Kod, along with a legal team from ClientEarth and 350.org. They argue that their way of life has come under immediate and irreversible threat.

On this basis, they accuse the Australian government of breaching multiple articles of the UN Human Rights Declaration, including the right to culture, the right to be free from arbitrary interference with privacy, family and home, and the right to life.

In the early 1990s, the Torres Strait Islands were at the centre of struggles to secure Aboriginal and Torres Strait Islander land rights in Australia.

Securing these rights were made possible through the historic Mabo Decision, and these rights remain central to land and human rights debates today as Torres Strait Islanders’ land and seas are threatened by climate change.

Torres Straight Islanders are on the frontlines

Some Torres Strait Islands are less than one metre above sea level and are already affected by climate change.

Rising tides have delivered devastating effects for local communities, including flooding homes, land and cultural sites, with dire flooding in 2018 breaking a sea wall built to protect local communities.

Thursday Island in the Torres Strait. The ancestral lands of these islands are being washed away by sea level rise from climate change.
Shutterstock

Increasing sea temperatures have also affected marine environments, driving coral bleaching and ocean acidification, and disrupting habitat for dugong, salt water crocodiles, and multiple species of turtle.

In the same way settler colonial violence dispossessed First Nations people from their ancestral homelands, climate change presents a real threat of further forced removal of people from their land and seas, alongside destruction of places where deep cultural and spiritual meaning is derived.

Parallel threats across the Pacific

While the Torres Strait appeal to the UN is groundbreaking, the challenges facing Torres Strait Islanders are not unique.

Delegates at the Pacific Islands Forum in Fiji last week described climate change as the “single greatest threat” to the region, with sea level rise occurring up to four times the global average in some countries in the Pacific.

Climate change is already causing migration across parts of the Pacific, including relocation of families from the Carteret Islands to Bougainville with support from local grassroots organisation Tulele Peisa.

The Alliance of Small Island States, an intergovernmental organisation, has demanded that signatories to the Paris Agreement, including through the Green Climate Fund, recognise fundamental loss and damages communities are facing, and compensate those affected.

The growing wave of climate litigation

Across the Torres Strait, the Pacific, and other regions on the frontline of climate change, there are a diversity of responses in defence of land and seas. These are often grounded in local and Indigenous knowledge.

They show the resolve of First Nations and local communities, as captured in a message from the Pacific Climate Warriors:

We are not drowning. We are fighting.

There are parallel appeals to the Torres Strait Islanders’ case. Around the world, First Nations people are calling on the UN to hold national governments to account on human rights obligations, including in the context of mining and other developments that drive greenhouse gas emissions.

In Australia, Wangan and Jagalingou Traditional Owners have submitted multiple appeals, including last year alleging government violations of six international human rights obligations in their effort to advance Adani’s proposed Carmichael mine.

There is an array of other climate litigation underway. This includes citizens suing their governments for failing to take action on climate, such as in the Netherlands, where a judge ordered the government to take hefty action to reduce national emissions.

Similarly, a group of 21 children in the United States are pursuing a lawsuit to demand the right to a safe climate.

Given the parlous state of climate politics in Australia, further litigation can be expected. The significance of the current appeal by a group of Torres Strait Islanders lies in its potential to lay bare the adequacy or otherwise of Australia’s response to climate change as a human rights issue.

First Nations people already have a moral authority in defending their human rights in the era of climate change. Over time, they and others, including children, will also test the grounds on which they might have the legal authority to do so.The Conversation

Kristen Lyons, Professor Environment and Development Sociology, The University of Queensland

This article is republished from The Conversation under a Creative Commons license. Read the original article.

How I discovered the Dalveen Blue Box, a rare eucalypt species with a sweet, fruity smell



Tim Collins classifying a new species of eucalyptus tree, Eucalytus dalveenica, March 2019.
University of New England, Author provided (No reuse)

Tim Collins, University of New England

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In 2002, I went on a bushwalk with plant taxonomist David Albrecht, and had a big surprise. He pointed to a plant I thought I knew, and said: “that’s probably a new species.”

A new species? How could it be that this plant had not already been scientifically described and named?

I was in for another surprise when I learnt there are estimated to be thousands of undescribed plant species in Australia. But just because one botanist says a plant is a new species, it doesn’t mean that everyone else automatically agrees.

As a researcher, I had the opportunity to study one of Australia’s most iconic plant groups – the eucalypts.

Herbarium records of an endagered eucalyptus species, the Northern Blue Box (Eucalyptus magnificata), showed populations from the Northern Tablelands in New South Wales scattered up to the Granite Belt in southern Queensland.



The Conversation

But on closer inspection, I discovered there were different ecosystems between populations. E. magnificata, for instance, is found on rims of gorges in Oxley Wild Rivers National Park, whereas E. baueriana is typically found on riverbanks and flood plains.

The question I wanted answered was: are all these populations really E. magnificata or have some been misidentified and represent other common species? Or, alternatively, are they new, undescribed rarer species?

So when my supervisors, Professor Jeremy Bruhl and Dr Rose Andrew, and I visited the mystery trees near Dalveen in southern Queensland, we knew immediately they were something exciting. They just looked different to everything else we’d seen.

Eucalyptus that smells sweet and fruity

To find out, I’d been sampling eucalyptus (collecting, pressing and drying specimens) and had spent the past two days with my supervisors. With our heads craned back, we stared through binoculars to search the tree canopy at dozens of sites on the Northern Tablelands looking for the buds and fruits that enable eucalypt identification.

Not only did these trees at Dalveen look unlike anything else we’d seen on the trip, they also had a different smell. When we crushed a leaf, the aroma was sweet, mild and fruity, quite unlike the familiar eucalyptus oil.

Back at the university, I could compare the different collections. I examined and recorded differences in the size and shapes of the leaves, buds and fruits. I grew seedlings of my field collections and saw that seedling leaves were also consistently different.

And I extracted the mixture of aromatic chemicals in the leaf oils collected during fieldwork. Then, I used a chemistry laboratory technique, called Gas Chromatography Mass Spectrometry, to compare their concentrations with closely related species, such as E. baueriana and E. polyanthemos.

The results clearly explained why the leaves had a unique scent. That sweet and fruity aroma was due to larger molecules, called sesquiterpenes, which dominated the leaf-oil. There were only traces of the familiar-smelling cineole molecule common to most eucalypts.

A new species, or just an uninhibited sex romp?

Sequencing the DNA of the tree added another piece to the puzzle.

We had collected samples from all of the closely related common species. We had strong evidence from the shape of the leaves, fruits and flower buds suggesting the Dalveen trees were different. But the possibility remained that they were just hybrids.

Eucalyptus trees can be wickedly promiscuous and hybrid trees with similar characteristics are common. In some parts of eastern Australia, for instance, eucalypts naturally form hybrid swarms, the botanical equivalent of a wildly uninhibited sex romp!

But the DNA told us the trees from Dalveen were genetically distinct, and with no suggestion of shared ancestry.

Now, with three very different data sets all supporting the same conclusion, it became imperative we publish our findings and describe the new species, which we named Eucalyptus dalveenica, or the Dalveen Blue Box.

New species have to be named using a universal and internationally accepted naming system. Names and descriptions must be published, and a pressed and dried specimen must be nominated to be the representative that other collections can be compared to.

Most importantly, convincing evidence must be presented that persuades the botanical community the newly named species should be accepted.

But naming a new species is only the first step in knowing what it is. Importantly, naming tells us what it isn’t. The trees at Dalveen are not Eucalyptus magnificata, nor do they belong to another more common species, E. baueriana or E. conica.

Eucalyptus dalveenica is a rare and endangered part of Australia’s natural heritage. Taxonomic description of new species (classifying, describing and naming) provides the framework for ongoing accurate identification, species conservation and further study.

We are fortunate to live in a beautiful part of the world, with diverse and unique wildlife. Describing biodiversity and communicating new discoveries develops connections between people and their local environment, leading to a broader understanding of our home.


Sign up to Beating Around the Bush, a series that profiles native plants: part gardening column, part dispatches from country, entirely Australian.The Conversation

Tim Collins, PhD candidate , University of New England

This article is republished from The Conversation under a Creative Commons license. Read the original article.