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A dust devil looks a bit like a tornado, but is weaker and rarely lasts more than about a minute.

It is a twisting column of warmed air scooting across sun-heated ground, made visible by the dust that it lofts upwards. Although usually benign, occasionally dust devils can kill.

Dust devils have been known to appear on Mars since the 1970s. They have been observed both from the ground and from orbit.

The more dust in the Martian atmosphere, the warmer and more agitated it becomes, and this can escalate into a global dust storm.

When the dust settles, it can coat and disable the solar panels that are essential for many of the instruments we’ve landed on the planet.

There’s a lot we don’t know about how these devils function. But new research, published this week in Nature Communications, has recorded what dust devils sound like – giving fresh insights into how they operate.

But it also raises questions about how future astronauts would detect and interpret sounds on the red planet.

There has been a vast amount of erosion on Mars since the last rivers and lakes vanished, including at the landing sites of both Nasa’s current rovers Curiosity and Perseverance.

Although the erosive power of an individual dust devil is tiny, a billion years worth of dust devils could potentially have worn away kilometres of rock.

There are thus many reasons for wanting to better understand how dust devils function.

And we now know what a Martian dust devil sounds like thanks to the new study led by Naomi Murdoch of Toulouse University in France.

Many passing dust devils have been imaged by cameras on Mars landers and rovers, but Murdoch and her team report a dust devil that luckily passed exactly over the Perseverance rover on September 27, 2021, which was on the floor of Jezero crater.

The rover’s masthead camera, named SuperCam, includes a microphone, and this recorded the sound of the wind rising and falling as the dust devil passed over.

In detail, the wind noise rose when the leading wall of the vortex arrived, followed by a lull representing the calm air in the eye of the vortex, before a second episode of wind noise as the trailing wall of the vortex passed over.

This took less than ten seconds, and you can hear the sound recording here(https://jirafeau.isae-supaero.fr/f.php?h=2JWSkdJR&p=1) (turn your volume to max). Other sensors gave information too. They showed that the pressure fell to a minimum between the two bursts of wind noise – which to me is consistent with sucking rather than blowing – and also recorded impacts of individual dust grains onto the rover.

The dust devil was about 25 metres in diameter, at least 118 metres tall, and was tracking across the ground at about five metres per second.

The maximum wind speed in the rotating vortex was probably just under 11 metres per second, equating to a “fresh” to “strong” breeze on Earth.

Did it really sound like that? Listening to a recording purporting to be the sound of Martian wind is all very well, but is this really what we would hear if we were there ourselves? The first thing to note is that this does genuinely originate as “real sound”, unlike other data such as images or radio signals turned into sound (a process known as sonification), such as the so-called sound of two black holes colliding or radio noise from from Venus’s atmosphere.

The dust devil audio file contains actual sound waves picked up by a microphone on Mars.

There the atmosphere is much thinner than on Earth (Martian surface pressure is less than a hundredth of ours), so the high frequency component of sound hardly carries (scientists say it’s “attenuated”).

The result is that the wind sounds much lower in pitch than a similar wind on Earth.

The only other planetary body from which we have genuine sound recordings is Venus, where in 1982 two Soviet “Venera” landers recorded wind and lander operation noises.

However, if you were on Mars you could never hear the wind directly with your own ears.

If you were foolish enough to expose your ears to Mars’s atmosphere, the low external pressure would cause your eardrums to burst, and you would be instantly deaf as well as having no air to breathe.

If you were to go outside in a pressurised spacesuit (a much more sensible idea), what you would hear would depend on how well the sound waves were transmitted through the solid shell of your helmet, and then on how these were turned back into sound waves in the air inside your helmet.

In other words, you would hear a distorted version of what an external microphone would pick up. Imagine walking round on Earth with your head inside a goldfish bowl and you’ll get part of the idea.

If future human explorers on Mars want to hear what’s going on in the external environment, I suspect they will rely on a suit-mounted microphone feeding to wireless ear buds, although I can’t find any evidence that that this has yet been factored into Mars suit design.

This all boils down to a recording from external microphone being the best way to represent sounds on Mars, or indeed any other planet that has an atmosphere.

If you want to hear some more sounds from Mars, NASA has a collection of audio recordings you can listen to.


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Astronomers Spot Galaxy NGC 3640 With a Past of Consuming Smaller Galaxies

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Astronomers Spot Galaxy NGC 3640 With a Past of Consuming Smaller Galaxies

An elliptical galaxy located 88 million light-years from Earth has been observed displaying unusual characteristics, with astronomers identifying it as a cosmic predator. The latest images captured by the Very Large Telescope (VLT) at the European Southern Observatory (ESO) indicate that the galaxy, designated NGC 3640, has a history of consuming smaller galaxies and may soon engulf another. The galaxy’s distorted structure and the faint, diffused light surrounding it serve as evidence of its turbulent past, as per reports. Positioned just above a smaller galaxy, NGC 3641, the larger body appears to be on a trajectory that could lead to a future merger. The study of such interactions provides insights into the evolutionary patterns of galaxies.

Evidence of Past Galactic Mergers

According to research published in Astronomy & Astrophysics, signs of previous mergers have been detected within NGC 3640. The structural distortions observed, coupled with the presence of older stellar populations, suggest that remnants of previously absorbed galaxies are embedded within its formation. Astronomers at the Italian National Institute for Astrophysics have analysed the remnants, with findings indicating that ancient stars from the original galaxy serve as markers of past collisions. The faint glow surrounding NGC 3640 is attributed to these past interactions, demonstrating the lasting effects of galactic mergers.

Upcoming Galactic Collision

Reports suggest that while NGC 3641 remains intact, its eventual fate may align with the ongoing patterns of NGC 3640. As galaxies interact, their gravitational forces distort their structures, often leading to eventual mergers. Current observations indicate no immediate impact on NGC 3641, implying that significant interactions have yet to begin. ESO officials have stated that galaxies undergo structural changes over time due to the absorption of gas and stars from their surroundings. This process has been linked to the unique shape and features displayed by NGC 3640.

Gravitational Influence and Cosmic Evolution

The gravitational forces exerted by approaching galaxies can trigger large-scale changes in their structures. Astronomers have been closely monitoring such interactions to gain a deeper understanding of galactic evolution. The observations made using the VLT provide an opportunity to study these cosmic processes in detail, with researchers continuing to track the potential merger between NGC 3640 and its smaller companion. The findings contribute to broader studies on the dynamic nature of galaxies and their role in shaping the universe over billions of years.

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Scientists Discover Declining Global Ocean Evaporation Amid Rising Temperatures

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Scientists Discover Declining Global Ocean Evaporation Amid Rising Temperatures

A decline in global ocean evaporation has been identified over the past decade, despite rising sea surface temperatures. This shift challenges established climate models, which have long linked higher temperatures to increased evaporation. The unexpected trend was observed through satellite data analysis, revealing that evaporation rates started decreasing after 2008. Researchers suggest that changing atmospheric circulation patterns and reduced wind speeds may be influencing this reversal, highlighting the complexity of Earth’s climate system.

Study Reveals Key Climate Anomalies

According to the study published in Geophysical Research Letters, an assessment of ocean heat flux data was conducted by researchers from the Institute of Geographic Sciences and Natural Resources Research at the Chinese Academy of Sciences. It was found that while ocean evaporation had been rising from 1988 to 2008, a reversal occurred thereafter, leading to a decline between 2008 and 2017.

The study’s lead author, Dr. Ma Ning, told Phys.org that two-thirds of the global oceans have shown reduced evaporation rates since the late 2000s. This decline contradicts previous expectations that global warming would consistently drive higher evaporation levels. The research suggests that large-scale atmospheric circulation shifts, particularly in the Northern Oscillation Index, may be contributing to the changes.

Impact of Wind Stilling on Evaporation

A decline in wind speed, referred to as “wind stilling,” has been identified as a crucial factor in this unexpected trend. Lower wind speeds result in reduced surface turbulence, thereby limiting the exchange of moisture between the ocean and the atmosphere. The study indicates that this phenomenon may be linked to broader climate oscillations affecting atmospheric circulation.

Dr. Ma explained that while evaporation levels have declined, this should not necessarily be viewed as a weakening of the global hydrological cycle. Instead, it may be an indication of natural climate variability influencing regional and global weather patterns. Researchers continue to investigate how these findings may affect long-term climate predictions.

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Arabia Had Five Times More Rainfall 400 Years Ago, Study Finds

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Arabia Had Five Times More Rainfall 400 Years Ago, Study Finds

Extreme rainfall in Arabia was five times more intense 400 years ago, as indicated by recent climate reconstructions. The data suggests that the region, currently defined by arid desert, once had significantly higher precipitation levels, resembling a lush savannah. The findings highlight the necessity for improved climate preparedness as urbanisation expands in the region.

Study Reveals Significant Rainfall Variability Over Centuries

According to the study published in Science Advances, researchers from the University of Miami Rosenstiel School of Marine, Atmospheric, and Earth Science discovered that the Arabian Peninsula had significantly higher rainfall over the last 2,000 years. The landscape, now barren, was once covered with vegetation and inhabited by wildlife such as lions, leopards, and wolves. Findings indicate that 200 years ago, rainfall was still double what it is today.

Deep-Sea Brine Pools Provide Uninterrupted Climate Record

As per reports, sediment cores were extracted from a deep-sea brine pool in the Gulf of Aqaba using a remotely operated vehicle (ROV) deployed from the research vessel OceanXplorer. The brine’s chemistry enabled the preservation of undisturbed sediment layers, allowing an accurate reconstruction of Late Holocene rainfall trends.

Implications for Climate Preparedness in the Middle East

Speaking to Phys.org, Sam Purkis, Professor and Chair of the Department of Marine Geosciences at the University of Miami Rosenstiel School, stated that the study underscores the importance of climate resilience as development projects like NEOM in Saudi Arabia reshape the region. The assumption of long-term climate stability is not reliable, according to Amy Clement, a Professor in the Department of Atmospheric Sciences at the same institution.

Urgency for Enhanced Flood and Drought Management

The Middle East, already vulnerable to extreme weather, faces rising instances of flash floods and droughts. The catastrophic flooding seen across the Arabian Peninsula in early 2024 reinforces the need to study historical rainfall patterns to improve disaster preparedness. Mattie Rodrigue, Science Program Director at OceanX, highlighted the importance of technological advancements in climate research to better predict future hydroclimate trends.

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