Stormy weather has threatened to delay the launch of Europe’s Hera spacecraft, which is scheduled to blast off on Monday, SpaceX has said.

The probe will head off on a mission to inspect the damage a NASA spacecraft did to an asteroid when it smashed into it in 2022 during the first test of Earth’s planetary defenses.

The Double Asteroid Redirection Test (DART) deliberately crashed into the pyramid-sized asteroid Dimorphos roughly 11 million kilometers (6.8 million miles) from Earth.

The fridge-sized spacecraft successfully knocked the asteroid well off course, demonstrating that humanity may no longer be powerless against potentially planet-killing asteroids that could head our way in the future.

But much about the impact remains unknown, including how much damage was done and exactly what the asteroid was like before it was hit.

So the European Space Agency (ESA) says it is sending Hera to the asteroid to conduct a “crime scene investigation” in the hopes of learning how Earth can best fend off future asteroids.

The spacecraft is scheduled to blast off on a SpaceX Falcon 9 rocket from Cape Canaveral in the US state of Florida at 10:52 am local time (1452 GMT) on Monday.

However thunderstorms have been forecasted in the launch area. SpaceX said on X on Sunday that the weather is currently only 15 percent favorable for a launch.

If a delay is required, a back-up launch is planned for Tuesday 10:46 am local time, SpaceX said.

The launch window for the mission will remain open until October 27.

Green light after ‘mishap’

The launch had also faced a potential delay due to an anomaly involving a Falcon 9 rocket during the launch of SpaceX’s Crew-9 astronaut mission late last month.

But on Sunday, the US Federal Aviation Administration gave the green light.

“The absence of a second stage re-entry for this mission adequately mitigates the primary risk to the public in the event of a reoccurrence of the mishap experienced with the Crew-9 mission,” it said in a statement.

The launch window for the mission will remain open until October 27.

Once launched, Hera is planned to fly past Mars next year and then arrive near Dimorphos in December 2026 to begin its six-month investigation.

Dimorphos, which is actually a moonlet orbiting its big brother Didymos, never posed a threat to Earth.

After DART’s impact, Dimorphos shed material to the point where its orbit around Didymos was shortened by 33 minutes—proof that it was successfully deflected.

Analysis of the DART mission has suggested that rather than being a single hard rock, Dimorphos was more a loose pile of rubble held together by gravity.

“The consequence of this is that, instead of making a crater” on Dimorphos, DART may have “completely deformed” the asteroid, the Hera mission’s principal investigator Patrick Michel told a press conference.

But there are other possibilities, he said, adding that the behavior of these low-gravity objects is little understood and “defies intuition”.

The 363-million-euro ($400 million) mission will be equipped with 12 scientific instruments and two nanosatellites.

© 2024 AFP

Mount Everest (also known as Chomolungma or Sagarmāthā) is famously the highest mountain in the Himalayas and indeed on Earth. But why?

At 8,849 meters above sea level, Everest is around 250m taller than the other great peaks of the Himalayas. It is also growing by about 2mm each year—roughly twice as fast as it has been growing on average over the long term.

In a paper published in Nature Geoscience, a team of Chinese and English scientists say Everest’s anomalous height and growth have been influenced by the Arun River, which flows through the Himalayas. They argue that the river’s course changed around 90,000 years ago, eroding away rock that was weighing Everest down—and the mountain has bounced up in response, by somewhere between 15 and 50m.

The authors make a case for the river’s contribution, but they acknowledge the “fundamental cause” of the peak’s size is the tectonic processes that create mountains. To understand what’s going on, we need to understand the forces that made the Himalayas in the first place, and the movements that let them grow so high.

The Tibetan blob

In the 19th century, British surveyors showed that the southern boundary of the Himalayan mountains accurately describes an arc that aligns precisely with a small circle on Earth. This is pretty amazing.

The only rational way it can be explained is if we have the Eurasian tectonic plate to the north, the Indian plate to the south, and in between a viscous mass (Tibet) spreading southwards as it slowly collapses under the force of gravity.

Deep down, the Tibetan plateau must be like hot syrup, with a cold crust at the higher levels displaying faults and earthquakes as it is pushed around by the slow northerly advance of the Indian tectonic plate. The exact nature and depth of this hot syrup is a matter of some debate, with geologists comparing it variously to creme brûlée and a jelly sandwich.

Overall, the collision of India and Eurasia is marked by a “megathrust fault,” where the Indian plate is gradually sliding under the Eurasian plate. The whole megathrust doesn’t move at the same time. In general, it lurches forward bit by bit in a series of “thrust earthquakes.”

Where the spreading mass of Tibet makes contact with India, we see a narrow band of these thrust earthquakes. It is what happens in that narrow band that ultimately determines the elevation of the world’s highest mountain.

How mountains rise (and fall)

Why is the Tibetan Plateau, to Everest’s north, so flat, whereas mountains abound next to this narrow band of quakes, where the collapsing mass couples with the advancing Indian subcontinent?

The answer lies in the way that the mass of a mountain is supported.

Imagine a mountain as a pile of rubble on a thin plastic table. There is no inherent strength in the tabletop, so it sags downwards and the pile of rubble sinks. Much like an iceberg, only a part of the mass sticks up.

Νow imagine a thicker strong plate at the edge of the table. Here the pile of rubble is supported by the flexural strength of the plate, so it can rise much higher above the surface. So here, mountains can be far higher. This is what happens where one tectonic plate slides over another, as the downgoing plate creates a stronger region.

Naturally, there is a balance. When the movement of tectonic plates causes earthquakes, the mountain tops can shatter and giant avalanches will move the fallen rock into the adjacent river systems.

The fall of this rubble may reduce the mountains’ absolute height, and also its relative height compared to neighboring valleys—though this will depend on how efficiently rivers move the debris downstream.

In turn, when this rocky mass is moved away downstream, the upstream areas will be somewhat lighter. In our plastic table model, we might expect the table surface would bow down less and rubble peak rise a smidgen higher.

This is what the new research argues, but fundamentally it is earthquakes that push mountains higher. When the megathrust ruptures, where the tectonic plates meet, up the mountains go—though how far up they go depends on the strength of the supporting rock beneath.

What’s special about Everest?

The crucial question (as indeed the authors recognize) is why does Everest stand out?

The boundary between collapsing Tibet and advancing India is defined by a giant megathrust fault. Some parts of this fault have not broken for a very long time, perhaps several centuries or more. It is likely that a lot of strain has accumulated in these areas, and when they finally break, the result will be catastrophic.

However, the part of the megathrust beneath Everest appears to break routinely, perhaps once or twice per century. The last big earthquake there partly involved an existing rupture.

With each break, it is likely that Everest grows a little higher. Hence, it’s no wonder that Everest is able to maintain its superiority in comparison to peaks in quieter parts of the megathrust.

As the new research suggests, rogue rivers may well play a role in Everest’s size—but the bulk of the mountain’s greater height still seems likely due to the pattern of quakes along the Himalayan fault.

The difficulty for the scientists involved is how to separate the individual contributions to height from different factors. One is erosional rebound, as the new research suggests, but there are also tectonic processes such as movement on the Main Central Thrust, or slow creep on the South Tibetan Detachment Fault beneath which Earth’s highest mountain has been exhumed.

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

Almost one-sixth of Earth’s land surface is covered in otherworldly landscapes with a name that may also be unfamiliar: karst. These landscapes are like natural sculpture parks, with dramatic terrain dotted with caves and towers of bedrock slowly sculpted by water over thousands of years.

Karst landscapes are beautiful and ecologically important. They also represent a record of Earth’s past temperature and moisture levels.

However, it can be quite challenging to figure out exactly when karst landscapes formed. In our new work published today in Science Advances, we show a new way to find the age of these enigmatic landscapes, which will help us understand our planet’s past in more detail.

The challenge

Karst is defined by the removal of material. The rock towers and caves we see today are what is left after water dissolved the rest during wet periods of the past.

This is what makes their age hard to determine. How do you date the disappearance of something?

Traditionally, scientists have loosely bracketed the age of a karst surface by dating the material above and beneath. However, this approach blurs our understanding of ancient climate events and how ecosystems responded.

Geological clocks

In our study, we found a way to measure the age of pebble-sized iron nodules that formed at the same time as a karst landscape.

This method has the technical name of (U/Th)-He geochronology. In it, we measure how much helium is produced by the natural radioactive decay of tiny amounts of the elements uranium and thorium in the iron nodules. By comparing the amounts of uranium, thorium and helium in a sample, we can very accurately calculate the age of the nodules.

We dated microscopic fragments of iron-rich nodules from the iconic Pinnacles Desert in Nambung National Park, Western Australia.

This world-famous site is renowned for its otherworldly karst landscape of acres of limestone pillars towering meters above a sandy desert plain. The Pinnacles form part of the most extensive belt of wind-blown carbonate rock in the world, stretching more than 1,000km along coastal southwestern WA.

We examined multiple microscopic shards of iron nodules that were removed from the surface of limestone pinnacles. These nodules formed in the soil that lay on top of the limestone during the period of intense weathering that created the karst. As a result, they serve as time capsules of the environmental conditions that shaped the area.

The big wet

We consistently found an age of around 100,000 years for the growth of the iron nodules. This date is supported by known ages from the rocks above and beneath the karst surface, proving the reliability of our new approach.

At the same time as chemical reactions caused growth of the iron-rich nodules within the ancient soil, limestone bedrock was rapidly and extensively dissolved to leave only remnant limestone pinnacles seen today.

From examining the entire rock sequence in the area, we think this period of intensive weathering was the wettest time in this part of WA over at least the past half a million years.

We don’t know what drove this increased rainfall. It may have been changes to atmospheric circulation patterns, or the greater influence of the ancient Leeuwin Current that runs along the shore.

Such a humid interval is in dramatic contrast to the recent droughts and increasingly dry climate of the region today.

Implications for our past

Iron-rich nodules are not unique to the Nambung Pinnacles. They have recently been used to track dramatic past environmental change elsewhere in Australia.

Dating these iron nodules will help to better document the dramatic fluctuations in Earth’s climate over the past three million years as ice sheets have grown and shrunk.

Understanding the timing and environmental context of karst formation throughout this time offers profound insights into past climate conditions, environments and the landscapes in which ancient creatures lived.

Climate changes and resulting environmental shifts have been crucial in shaping ecosystems. In particular, they have had a profound influence on our ancient hominin and human ancestors.

By linking karst formation to specific climatic intervals, we can better understand how these environmental changes may have affected early human populations.

Looking forward

The more we know about the conditions that led to the formation of past landscapes and the flora and fauna that inhabited them, the better we can appreciate the evolutionary pressures that shaped the ecosystems we see today. This in turn offers valuable information for preparing for future changes.

As human-driven climate change accelerates, learning about past climate variability and biosphere responses equips us with knowledge to anticipate and mitigate future impacts.

The ability to date karst features with greater precision may seem like a small thing—but it will help us understand how today’s landscapes and ecosystems might respond to ongoing and future climate changes.

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