Glass beads in lunar soil reveal ancient asteroid bombardments on the moon and Earth

Hexbyte Glen Cove

Credit: NASA / JSC

In 2020, China’s Chang’e 5 mission sampled more than a kilogram of moon rock and soil and brought it back to Earth. The samples contain countless tiny beads of glass, created when asteroids hit the moon and splashed out droplets of molten rock around the impact site.

We have analyzed these and the near where they were found in great detail. Our results, published in Science Advances, reveal new details about the history of asteroids hitting the moon over the past 2 billion years.

In particular, we found traces of several waves of impacts occurring at the same times as impacts on Earth—including the Chicxulub impact 66 million years ago that led to the extinction of the dinosaurs.

Billions of years of space rocks

The destructive power of meteorite impacts has been seen throughout human history. Recently notable event from 2013, the spectacular Chelyabinsk meteor that injured hundreds of people, was a relatively minor occurrence compared to historical impacts.

Impacts of various scales have happened throughout Earth’s long geological history. Only about 200 impact craters have been found around the world, because erosion and geological activity are constantly modifying our planet’s surface and erasing evidence of past impacts.

On the moon, where impact craters don’t go away, several hundred million are recognizable. It is not difficult to imagine Earth experienced a similar staggering barrage of projectiles early in its life.

As the solar system evolved over the last 4.5 billions of years, the number of asteroids declined exponentially over time as space rocks were swept up by Earth and the other planets.

However, the details of this process remain murky. Was there a smooth decay over time in the number of impacts on Earth, moon and other planets in the solar system? Are there periods when collisions became more frequent, against this general background of decline? Is there a possibility that collisions may suddenly increase in the future?

Splattered glass

The best available place to search for answers is the moon, and the best available samples are lunar soils—like the ones Chang’e 5 brought home.







The Chelyabinsk meteor was small potatoes by historical meteor standards. Credit: Alexander Ivanov / Wikimedia, CC BY

Lunar soil contains spherical droplets of solidified melt (glass) with sizes ranging from a few millimeters to less than a millimeter. These droplets are formed during high-speed impacts that melt the target rock.

The melted droplets can splash out for tens or possibly hundreds of kilometers around the .

By analyzing the chemical makeup and radioactivity of these droplets, we can determine how old they are. The ages of the droplets then gives us an indication of when these impacts happened on the moon.

Each lunar soil sample appears to record multiple impacts. The ages of the impacts are spread over the past ~4 billion years, with the youngest being only a few million years old.

A simple landing site

Chang’e 5 landed at a site with a relatively simple geological history, compared to other sites on the moon where samples have been collected.

The is in the middle of a vast basaltic plateau nearly 400 kilometers across. The plateau is “only” 2 billion years old, which is young relative to the age of the lunar crust overall.

This means the history of the site is shorter and simpler to unravel. This made it easier to identify droplets originating from nearby impacts, as well as interpreting chemical and chronological data via satellite images of the surrounding lunar surface.

We combined this interpretation with modeling of how the droplets would have formed and splashed out in impacts of different sizes.

It appears that glass droplets can be transported for 20 to 100 kilometers from the site of impacts, even when the impact leaves a only 100 meters across. Models also indicate that impacts forming craters more than 1 kilometer across are more efficient in producing the droplets.

All this information combined helped to initiate the search for specific impact craters responsible for the production of glasses extracted from the sample.

Glass droplets from the lunar soil reveal a history of asteroid impacts. Credit: Beijing SHRIMP Center, Institute of Geology, Chinese Academy of Geological Sciences, Author provided

Crater hunting

The basaltic plateau surrounding Chang’e 5’s landing site contains more than 100,000 craters over 100 meters in size. Matching glass droplets with their crater of origin is a probability game, though the odds are a little better than winning the lottery.

We can say some of the craters are likely to be the source of some of the glass droplets in the sample. Nevertheless, this matching led to another important outcome.

Previous studies had found the distribution of ages of glass droplets in the individual soil samples is uneven. There are periods in the timeline with large numbers of droplets and periods with few to none.

Our analysis of glass in the Chang’e 5 samples and our attempts to link them to specific craters confirms a variation in impact rate through time.

In addition, the ages of the periods identified from these appear to be similar to those visible in a number of existing meteorite groups originating in the asteroid belt. These meteorite groups may be the results of ancient collisions within the asteroid belt.

One of these cluster ages also coincides with the dinosaur extinction. Our study did not examine this in detail, but this coincidence may indicate that, for reasons yet unknown, there are periods when regular orbits of small bodies in the solar system destabilize and head into orbits where they may hit the Earth or moon.

Taken together, these ages suggest there may have been periods of time over Earth’s history when collisions increased throughout the inner . This means Earth could have also experienced periods when rate of impacts was higher than usual—and that similar increases are possible in the future.

How would such an increase affect the evolution of life on the planet? That remains a mystery.



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

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Bioeconomy and carbon neutrality: ‘Without further investments we will miss the target’

Hexbyte Glen Cove

Credit: Unsplash/CC0 Public Domain

“Without further investments in the bioeconomy, the net zero emission target will not be met.” Data issued from the EU project Biomonitor point out gaps in the Green Deal and suggest speeding up procedures states, “New technologies must be fostered but length and complexity of the European approval process risk discouraging the investors.”

“To achieve carbon neutrality by 2050 we need more investments than those envisaged by the Green Deal, otherwise we will never make it. It is crucial that the European Commission further stimulates the bio-economy and does not drive away investors.”

This is not critics, nor politicians speaking, but the figures issued by an EU project which modeled several possible scenarios for the next decades. Lasting over four years, Biomonitor kicked off in 2018 with the aim of addressing the information gap in research, to provide political and economic leaders with more effective planning tools. Justus Wesseler is the project coordinator.

What strategies do the data suggest for achieving the zero emission target by 2050, set by the European Green Deal?

First of all you need to increase investments in the bio-economy. And then you have to make the new technologies ready for use earlier than they are today.

Why are these two steps so crucial?

The bioeconomy can substantially contribute to achieving , but it will not be allowed to play such a key role without further technological changes. That is why the data suggest that we need more investments. Those currently indicated by the Green Deal will not be enough to meet the target of climate neutrality by 2050.

What other scenarios have you taken into account?

One is just continuing business as usual and it would basically result in replicating in the future what has happened so far. A second scenario envisages an extreme strengthening of the bioeconomy, via dedicated investment policies and another one the possible impacts of the introduction of taxes on carbon dioxide.

What do you suggest, then?

It is not up to us, scientists and researchers, to suggest what should be done, but we can say: “Hey, look at our results and see what may happen if you do either this or that.” Our data and scenarios can just provide inputs for and European institutions to speed up the implementation of the bioeconomy and point out where further adjustments can be made.

For instance?

It depends on goals and priorities. But at the EU level, for example, it might be helpful to direct the investments towards specific sub-sectors of the bioeconomy where the potential for reducing is higher than for others.

Are you then satisfied by the outcome of the Biomonitor project?

Yes, definitively. At the beginning we faced a kind of blank page. Back in 2018 we lacked a lot of information on the development of the European bioeconomy and its implications for sustainability. Which means implications for the greenhouse gas emissions, for the biodiversity but also for the labor market. Re-structuring data has not been easy, especially in some bio-economy sub-sectors characterized by the presence of just a few stakeholders. Additionally, due to the data protection regulation, some of them are only available at the aggregate level. But despite the challenges, I’m very satisfied because we managed to achieve some very relevant results.

What is the one you are most proud of?

We have developed better methods for assessing the sustainability of the bioeconomy, which can now be used by different stakeholders: EU policy makers, member states, private companies. Some information was already there, but we helped to better organize the data and to make it available for further assessment.

Is the job is done, then?

Far from it. Our objective was just to pave the way for a much longer journey. We identified the data gaps, but it was not up to us to fill them. We just provided methodologies which can now be picked up by different stakeholders.

Paving the way for the bio-economy also means embracing a new mindset. Do you think time is now ripe for that?

When Biomonitor kicked-off, the mindsets were not ready for it. But due to the war in Ukraine, everything changed very quickly. Policy makers and citizens have become much more aware of how dependent we are on other regions of the world, with respect in particular to energy supplies. They have understood that we do need to use energy more sustainably. And at this extent the bioeconomy can be crucial. It can help improve the use of biological resources and converting them into energy, but also into other useful bio-based products, which might help reduce our dependency on Russia.

You have mentioned the war in Ukraine and the spike in energy prices: how will such a geopolitical context affect the implementation of the bioeconomy?

It is of course quite a challenge. The effects will be positive and negative at the same time. On the one hand, the Ukrainian crisis has shown us how important sustainable are for the European Union. Generating energy from biological resources will become more important and this will foster the investments and support the development of the bioeconomy. On the other hand, some bio-based products are already affected by the rise in energy prices and this might discourage consumers.

Some critics argue that lots of sustainable solutions are still quite expensive today, thus slowing down the implementation of the bioeconomy.

Some solutions may still be a little more expensive, but this just proves that we need more progress and more investments to scale them up. Over time, costs and prices will go down as they always do when you develop new technologies. And then, look at what Tesla achieved: their cars might still be just for big spenders, but they basically forced the whole car industry to follow and increase in electric cars.

Let’s finish with a tip for the future.

Our data also showed that the length and complexity of the approval process for new technologies are extremely expensive for companies and end up discouraging investors. On a very concrete basis, the European Commission could, for instance, reduce such time frames and, in doing so, stimulate the development of the bioeconomy. It would cost nothing and only require political will. It’s in their hands.



More information:
Biomonitor: biomonitor.eu/

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