The anatomy of a planet

The anatomy of a planet

Since early 2019, researchers have been recording and analysing marsquakes as part of the InSight mission. This relies on a seismometer whose data acquisition and control electronics were developed at ETH Zurich. Using this data, the researchers have now measured the red planet’s crust, mantle and core - data that will help determine the formation and evolution of Mars and, by extension, the entire solar system.

Mars once completely molten

We know that Earth is made up of shells: a thin crust of light, solid rock surrounds a thick mantle of heavy, viscous rock, which in turn envelopes a core consisting mainly of iron and nickel. Terrestrial planets, including Mars, have been assumed to have a similar structure. “Now seismic data has confirmed that Mars presumably was once completely molten before dividing into the crust, mantle and core we see today, but that these are different from Earth’s,” says Amir Khan, a scientist at the Institute of Geophysics at ETH Zurich and at the Physics Institute at the University of Zurich. Together with his ETH colleague Simon Stähler, he analysed data from NASA’s InSight mission, in which ETH Zurich is participating under the leadership of Professor Domenico Giardini.

No plate tectonics on Mars

The researchers have discovered that the Martian crust under the probe’s landing site near the Martian equator is between 15 and 47 kilometres thick. Such a thin crust must contain a relatively high proportion of radioactive elements, which calls into question previous models of the chemical composition of the entire crust.

Beneath the crust comes the mantle with the lithosphere of more solid rock reaching 400-600 kilometres down - twice as deep as on Earth. This could be because there is now only one continental plate on Mars, in contrast to Earth with its seven large mobile plates. “The thick lithosphere fits well with the model of Mars as a ‘one-plate planet’,” Khan concludes.

The measurements also show that the Martian mantle is mineralogically similar to Earth’s upper mantle. “In that sense, the Martian mantle is a simpler version of Earth’s mantle.” But the seismology also reveals differences in chemical composition. The Martian mantle, for example, contains more iron than Earth’s. However, theories as to the complexity of the layering of the Martian mantle also depend on the size of the underlying core - and here, too, the researchers have come to new conclusions.

The core is liquid and larger than expected

The Martian core has a radius of about 1,840 kilometres, making it a good 200 kilometres larger than had been assumed 15 years ago, when the InSight mission was planned. The researchers were now able to recalculate the size of the core using seismic waves. “Having determined the radius of the core, we can now calculate its density,” Stähler says.

“If the core radius is large, the density of the core must be relatively low,” he explains: “That means the core must contain a large proportion of lighter elements in addition to iron and nickel.” These include sulphur, oxygen, carbon and hydrogen, and make up an unexpectedly large proportion. The researchers conclude that the composition of the entire planet is not yet fully understood. Nonetheless, the current investigations confirm that the core is liquid - as suspected - even if Mars no longer has a magnetic field.

Reaching the goal with different waveforms

The researchers obtained the new results by analysing various seismic waves generated by marsquakes. “We could already see different waves in the InSight data, so we knew how far away from the lander these quake epicentres were on Mars,” Giardini says. To be able to say something about a planet’s inner structure calls for quake waves that are reflected at or below the surface or at the core. Now, for the first time, researchers have succeeded in observing and analysing such waves on Mars.

“The InSight mission was a unique opportunity to capture this data,” Giardini says. The data stream will end in a year when the lander’s solar cells are no longer able to produce enough power. “But we’re far from finished analysing all the data - Mars still presents us with many mysteries, most notably whether it formed at the same time and from the same material as our Earth.” It is especially important to understand how the internal dynamics of Mars led it to lose its active magnetic field and all surface water. “This will give us an idea of whether and how these processes might be occurring on our planet,” Giardini explains. “That’s our reason why we are on Mars, to study its anatomy.”

References

Khan A et al.: Upper mantle structure of Mars from InSight seismic data. Science, 373, (6553) p. 434-438. 10.1126/science.abf2966

Stähler S et al.: Seismic detection of the Martian core.

Science, 373, (6553) p. 443-448. doi:10.1126/science.abi7730

Knapmeyer-Endrun B et al.: Thickness and structure of the Martian crust from InSight seismic data. Science, 373, (6553) p. 438-443. doi:10.1126/science.abf8966

Republication: Beyond Bitcoin: Ethereum and DeFi

Feature Stories | Jun 28 2021

In Part III of FNArena’s exploration of crypto currency, we examine the rise of Ethereum, and the implications of Ethereum’s far more extensive application capacity. An error in the original publication has now been addressed

Apologies. In the previous publication the label “proof of stake” was erroneously labelled as “proof-of-scale”. That error has been seen to in this republication. This story was originally published on June 6, 2021.

-Drawbacks to bitcoin

-The proof-of-sake model

-The rise of DeFi on the Ethereum platform

-The risks for Ethereum

By Greg Peel

This is the third part in FNArena’s series on the world of crypto. Part I explains just what bitcoin is and how it works. Part II compares bitcoin and gold as stores of wealth. Links below.

Proof of Work

As explained in the first part of this series, bitcoin is backed by the blockchain ledger system. Critical to bitcoin’s existence is the verification of each block in the chain, which is provided by solving a complex algorithm available in “open source”, and which does not require a superior brain but rather the capacity to run bllions of calculations to arrive at the right answer.

This process is known as “mining”, as the reward for verification of a block is an amount of new bitcoin. Given the work involved in bitcoin mining (by computers), the process of verification is known as “proof of work”.

The onerous proof-of-work process is what provides bitcoin with its capacity to be a store of wealth – what makes bitcoin sufficiently “rare”. It is rarity that underpins the world’s traditional store of wealth – gold. Not only is gold hard to find to begin with, the cost involved in exploration, mining and processing also underpins its value.

Bitcoin mining also comes at a cost – being that of significant energy usage required to successfully mine a bitcoin.

Bitcoin dominates the crypto-currency market due to first mover advantage. The creators of bitcoin first created the blockchain system, which, being “open source”, is universally available to anyone. Hence there are now some 8000 crypto-currencies, and growing. Bitcoin enjoys the unquantifiable “brand awareness” factor, which helps to underpin its value.

And being the first, it has a 12-year track record. In all that time, no one has been able to hack into bitcoin – into the blockchain. This is a primary selling point of crypto. And because it is a decentralised peer-to-peer system, it is not subject to regulation.

Yet.

The issue of regulation has become more pressing in recent weeks. Bitcoin may not be able to be hacked, but nor is it able to prevent “bad actors” from using it as an untraceable currency perfect for money laundering. Indeed, wholly suitable for criminal activity.

Ransomware attacks on the Colonial oil pipeline, and JBS Meats – the US and world’s largest meat packer/distributor – have brought this problem to the fore, and they represent just two high profile cases among many others. By demanding payment in bitcoin, hackers ensure those funds cannot be traced to their destination.

Or so they thought. Enter the recently formed US Department of Justice Ransomware & Digital Extortion Taskforce. It was able to recover a majority of the millions of dollars equivalent paid in bitcoin to the DarkSide network responsible.

Bitcoin supporters were somewhat shocked to hear this news. In the world of real dollars, beating criminals would be lauded by everyone other than the criminals. In crypto-world, the fact the DoJ was able to find and recover bitcoins rather brings into question all that crypto is meant to be. The dollar price of bitcoin fell on the news.

So we could list bitcoin’s major problems/threats as being energy intensity, regulation (both in investor protection and crime prevention) and, given the number of crypto-currencies now out there, competition.

Proof of Stake

There may still be daylight in between, but emerging as the biggest rival to bitcoin is ether, the crypto-currency behind the Ethereum platform. But while bitcoin and ether might be competing currencies, Bitcoin (the platform) and Ethereum do offer significant differences.

Like Bitcoin, Ethereum runs on a proof-of-work basis. Hence ether can be mined in the same fashion as bitcoin. Unlike bitcoin, ether is open-ended. As the pool of bitcoin grows, the number of bitcoins provided as reward for successful mining halves at intervals, and once that pool reaches 21 million, no further bitcoin will be released. At the current pace, forecasts are for this to occur around 2040.

The reward for successful ether mining is fixed at 5 ether, and there is no ultimate limit. One might suggest this instinctively makes bitcoin a more valuable longer term investment, but for Ethereum, the ether currency is only part of the story.

Ethereum was established in 2015 – six years behind Bitcoin. Rather than being a simple copy-cat, Ethereum was designed to be much more than just a payment system. In the creators’ own words, it is a “decentralised platform that runs smart contracts: applications that run exactly as programmed without any possibility of downtime, censorship, fraud or third party interference”.

Ethereum is also in the process of migrating from a proof-of-work model to a “proof-of-stakee” model.

In a proof-of-stake model, there is no mining, and thus no excessive draw on energy. Rather than miners, there are “validators”. There is no complex algorithm to solve. Instead, to be rewarded, validators must first own ether (in Ethereum’s case) and then put that ether balance on the line to certify that a block is valid.

This way, any malicious activity will result in that ether balance being lost.

And whereas miners of bitcoin receive bitcoins as a reward for their verification of blocks, validators of ether will simply receive a fee for every transaction and smart contract they validate. On the other side of the ledger, the parties that want a transaction or smart contract to be executed will pay a fee to have it completed and added to the blockchain.

Proof-of-stake in theory removes two of the proof-of-work model’s major drawbacks, being energy intensity and the potential for malicious activity such as the recent ransomware demands made on the Colonial Pipeline, JBS meats and others.

As Creighton University (US) academics suggest, “Bitcoin is striving to provide fast and secure transactions while Ethereum is focusing on much more. As more and more smart contracts and decentralised applications are built, Ethereum’s popularity and profitability will increase”.

Both currencies remain volatile at this point, but ether is still relatively new. And Ethereum’s migration to the proof-of-stake model is still pending, with guidance remaining vague at this point. It could yet take a while.

Unlocking the power of the microbiome

Hundreds of different bacterial species live in and on leaves and roots of plants. A research team led by Julia Vorholt from the Institute of Microbiology at ETH Zurich, together with colleagues in Germany, first inventoried and categorised these bacteria six years ago. Back then, they isolated 224 strains from the various bacterial groups that live on the leaves of thale cress (Arabidopsis thaliana). These can be assembled into simplified, or “synthetic” plant microbiomes. The researchers thus laid the foundations for their two new studies, which were just published in the journals Nature Plants and Nature Microbiology.

Volume control of the plant response

In the first study, the researchers investigated how plants respond to their colonisation by microorganisms. Vorholt’s team dripped bacterial cultures onto the leaves of plants that had, up to that point, been cultivated under sterile conditions. As expected, different types of bacteria triggered a variety of responses in the plants. For example, exposure to certain genera of Gammaproteobacteria caused the thale cress plants to activate a total of more than 3,000 different genes, while those of Alphaproteobacteria triggered a response in only 88 genes on average.

“Despite this broad range of responses to the different bacteria of the microbiome, we were astonished to pinpoint a central response: the plants practically always activate a core set of 24 genes,” Vorholt says. But that’s not all the team found: acting as a kind of volume control for the plant response, the activation intensity of these 24 genes provides information as to how extensively the bacteria have colonised the plant. This volume control also predicts how many additional genes the plant will activate as it adapts to the new arrivals.

Plants with defects in some of these 24 genes are more susceptible to harmful bacteria, Vorholt’s team has shown. And since other studies had noticed that some genes in the core set are also involved in plant responses to osmotic shock or fungal infestation, the ETH researchers infer that the 24 genes constitute a general defensive response. “It looks like an immune training, even though the bacteria we used aren’t pathogens, but rather partners in a natural community,” Vorholt says.

Bacterial community out of control

In the second study, Vorholt and her team explored how bacterial communities change when mutations cause a plant to be deficient in one or several genes. The team expected to see that genetic defects in receptors, which plants use to detect the presence of microbes, play a major role in the story.

What they didn’t expect was that another genetic defect would have the biggest effect: if the plants were deficient in a certain enzyme, an NADPH oxidase, the bacterial community was thrown off-?kilter. Plants use this enzyme to produce highly reactive oxygen radicals, which have an antimicrobial effect. In the absence of this NADPH oxidase, microbes that under normal circumstances lived peacefully on the leaves developed into what are known as opportunistic pathogens.

Is the NADPH oxidase found among the core set of 24 genes responsible for general defensive response? “No, that would have been too good to be true,” says Sebastian Pfeilmeier, a member of Vorholt’s research group and lead author of the study. This is because the gene responsible for the NADPH oxidase is turned on prior to contact with microbes and because the enzyme is activated by chemical reactions governed by phosphorylation.

For Vorholt, the two studies show that synthetic microbiomes are a promising approach to investigating the complex interactions within different communities. “Since we can control and precisely engineer the communities, we can do much more than just observe what happens. In addition to simply determining cause and effect, we can understand them on a molecular level,” Vorholt says. An ideal microbiome protects plants from diseases while also making them more resilient to drought and salty conditions. This is why the agricultural industry is among those interested in the team’s results. They should help farmers harness the power of the microbiome in the future.