S27E54: Earth's Ancient Shield: Unearthing the Origins of Our Magnetic Field

[00:00:00] This is SpaceTime Series 27 Episode 54 for broadcast on the 3rd of May 2024

[00:00:07] Coming up on SpaceTime, the oldest evidence shed for Earth's magnetic field.

[00:00:13] Scientists find Jupiter's moon Io has always been volcanic.

[00:00:17] And how Eclipse projects a shedding new light on the solar corona.

[00:00:22] All that and more coming up on SpaceTime

[00:00:26] Welcome to SpaceTime with Stuart Gary

[00:00:30] Geologists have uncovered ancient rocks in Greenland that bear the oldest remnants of Earth's magnetic field ever found.

[00:00:52] The findings reported in the Journal of Geophysical Research show that these rocks appear to be exceptionally pristine

[00:00:58] despite having preserved their properties for some 3.7 billion years.

[00:01:03] The authors have determined that the rocks retain signatures of a magnetic field with a strength of at least 15 microtesla

[00:01:10] and that similar in magnitude to the Earth's magnetic field today.

[00:01:14] The discovery potentially extends the age of the Earth's magnetic field by hundreds of millions of years.

[00:01:20] The study's authors say the findings may shed light on the planet's early conditions

[00:01:24] which helped form life and allowed it to take a hold.

[00:01:28] One of the study's authors, Claire Nichols from Oxford University says the magnetic field is in theory at least

[00:01:33] one of the reasons Earth is unique as a habitable world in our solar system.

[00:01:38] You see, the magnetic field protects life on Earth from harmful radiation from space

[00:01:43] and from the constant erosion of the atmosphere by the solar wind.

[00:01:47] A stream of charged particles continuously flowing out from the sun.

[00:01:51] But simply it helps retain the oceans and atmospheres essential for life as we know it for long periods of time.

[00:01:58] Previous studies had shown evidence for a magnetic field on Earth that's at least three and a half billion years old

[00:02:03] and this new study extends that significantly by a further 200 million years.

[00:02:08] The study's co-author Benjamin Weiss says it's important because that's the time when scientists think life was emerging on Earth.

[00:02:16] Weiss says if the Earth's magnetic field was around a few hundred million years earlier

[00:02:20] it could have played a crucial role in making the planet habitable.

[00:02:24] Today Earth's magnetic field's powered by its molten iron core

[00:02:28] which slowly churns up electric currents and is self-generating geodynamo.

[00:02:33] The resulting magnetic field extends out and around the planet like a protective shield.

[00:02:38] Scientists suspect that early in the planet's evolution

[00:02:41] the Earth was able to foster life in part due to an early magnetic field that was strong enough

[00:02:46] to retain a life-sustaining atmosphere and simultaneously shield the planet from damaging solar radiation.

[00:02:52] However, exactly how early and robust this magnetic field was

[00:02:56] has long been a subject of debate among scientists.

[00:03:00] In 2018, Nicholson colleagues undertook an expedition to the Isua Supercrustle Belt

[00:03:05] a 40-kilometre-long stretch of exposed rock formations surrounded by towering ice sheets

[00:03:11] in the rugged and isolated southwestern part of Greenland.

[00:03:15] There, scientists discovered some of the oldest preserved rocks on Earth

[00:03:19] which have since been extensively studied in hopes of answering a slew of questions about Earth's ancient environment.

[00:03:25] For Nicholson Weiss, the objective was to find rocks that still held their signatures

[00:03:30] of the Earth's early magnetic field, which was imprinted on the rocks when they first formed.

[00:03:35] Of course, sedimentary rocks form over millions of years as grains of sediment and minerals accumulate

[00:03:40] and progressively pack together in a buried under subsequent deposition over time.

[00:03:46] Any magnetic minerals such as iron oxides that are in these deposits

[00:03:49] follow the pull of the planet's magnetic field as they form.

[00:03:53] This collective orientation and the imprint of the magnetic field it has

[00:03:57] are therefore preserved in the rocks.

[00:04:00] Problem is, this preserved magnetic field can be scrambled and completely erased

[00:04:04] if the rocks subsequently undergo extreme thermal or aqueous events

[00:04:08] such as hydrothermal activity or plate tectonics that can pressurize and crush the deposits.

[00:04:13] Determining the age of a magnetic field in ancient rocks

[00:04:16] is therefore developed into a highly contested area of study.

[00:04:20] To get to rocks that were hopefully preserved and altered since their original deposition

[00:04:24] the authors sampled from rock formations in the Asiua Supercrustal Belt

[00:04:28] a remote location right up against the ice sheet which is only accessible by helicopter.

[00:04:33] The expedition returned to the lab with whole rock samples of banded iron formations.

[00:04:38] That's a type of rock that appears as stripes of iron rich and silica rich rock.

[00:04:43] The iron oxide minerals found in these rocks can act as tiny magnets

[00:04:47] that orient with any external magnetic field.

[00:04:50] Now given their composition the authors suspect that these rocks were originally formed

[00:04:54] in primordial oceans prior to the rise in atmospheric oxygen levels

[00:04:58] around two and a half billion years ago.

[00:05:01] Back then there wasn't oxygen in the atmosphere so the iron didn't oxidize easily.

[00:05:06] Instead it remained in solution in the oceans until it reached a critical concentration

[00:05:11] and then it simply precipitated out.

[00:05:14] Nikol says the iron raining down out of the oceans was deposited on the sea floor

[00:05:18] eventually becoming part of the rocks they recovered.

[00:05:21] Previous studies used uranium lead dating to determine the age of the iron oxides in these rock samples.

[00:05:27] The ratio of uranium to lead gave scientists an estimate of the rocks age.

[00:05:32] Uranium gradually radioactively decays into lead because scientists know that half-life of uranium

[00:05:38] it gives them an estimate of the rocks age.

[00:05:41] And the analysis found that some of these magnetized minerals were likely to be around 3.7 billion years old.

[00:05:47] Now the authors had already shown that the uranium to lead age also dates the age of the magnetic record in these minerals.

[00:05:53] So they then set out to determine whether the ancient rocks preserved magnetic fields from that far back

[00:05:59] and if so how strong that magnetic field might have been back then.

[00:06:03] Now to do this the samples are firstly demagnetized

[00:06:07] and then slowly remagnetized at known levels allowing scientists to compare the gradient

[00:06:12] of the demagnetization to the gradient of the remagnetization in the lab.

[00:06:16] And that gradient tells you how strong the ancient magnetic field originally was.

[00:06:21] This allowed the team to establish that the rocks likely harbored an ancient 3.7 billion year old magnetic field

[00:06:27] with a magnitude of at least 15 micro Tesla.

[00:06:30] Now today Earth's magnetic field measures around 30 micro Tesla.

[00:06:35] So that's half the strength but the same order of magnitude.

[00:06:38] The fact that it's of similar strength as today's field implies that whatever is driving Earth's magnetic field

[00:06:43] hasn't changed massively in power over billions of years.

[00:06:47] The team's experiments also showed that the rocks retained their ancient magnetic field

[00:06:51] despite having undergone two subsequent thermal events.

[00:06:55] Any extreme thermal event such as a tectonic shakeup of the substructure

[00:06:59] or hydrothermal eruptions could potentially heat up and erase the rocks magnetic field.

[00:07:05] The authors found that the iron in the samples likely oriented

[00:07:08] and then crystallized 3.7 billion years ago in some initial extreme thermal event.

[00:07:14] Then around 2.8 billion years ago and again one and a half billion years ago

[00:07:18] the rocks may have been reheated but not to the extreme temperatures

[00:07:22] that would have scrambled their magnetization.

[00:07:25] These results also raised questions about how the ancient Earth could have powered such a robust magnetic field.

[00:07:31] While today's field is powered by crystallization of the solid iron inner core

[00:07:35] it's thought that the inner core had not yet fully formed so early in the planet's evolution.

[00:07:40] Vice concludes that it seems whatever was generating a magnetic field back then

[00:07:45] was a different power source to what's generating it today.

[00:07:49] That raises some interesting questions.

[00:07:52] This is space time.

[00:07:54] Still to come.

[00:07:55] Scientists find Jupiter's moon Io's always been volcanic

[00:07:59] and Eclipse projects shedding new light on the solar corona.

[00:08:03] All that and more still to come on space time.

[00:08:07] A new study has shown that Jupiter's Galilean moon Io has always been volcanic.

[00:08:27] The findings reported in the journal Science show that sulfur and chlorine isotopes in Io's atmosphere

[00:08:33] indicate that it's been volcanically active for its entire 4.57 billion years of existence.

[00:08:40] The findings are offering new insights into the moon's history.

[00:08:44] Io is the most volcanically active body in our solar system.

[00:08:48] This extreme level of volcanic activity is the result of massive tidal heating

[00:08:53] from friction generated within the moon's interior as it's constantly stretched and squeezed

[00:08:58] by the gravitational pull of Jupiter and its neighbouring moons Europa and Ganymede.

[00:09:03] However, how long ago Io hosted such extensive volcanism has never been fully understood.

[00:09:09] Due to the moon's current level of volcanic activity, the surface of Io is constantly being reworked.

[00:09:15] On Io, instead of weather reports, you'd have geology reports.

[00:09:19] With mountain building in the east, volcanic lava lakes in the west,

[00:09:23] fresh eruptions in the north and tectonic upheavals in the south.

[00:09:27] All this leaves a geological record at most just a million years or so old.

[00:09:33] So instead, stable isotopic measurements of volatile elements in Io's atmosphere

[00:09:38] are being looked at because they could provide information about the history of volcanism on Io.

[00:09:43] So a team led by Catherine DeClaire from Caltech, the California Institute of Technology

[00:09:48] used ALMA, the Atacama Large Millimetre Sub-Millimeter Array Radio Telescope in Chile

[00:09:53] to observe the gases in Io's tenuous atmosphere and use them

[00:09:57] to determine the stable isotopic ratios of sulfur and chlorine bearing molecules.

[00:10:02] The authors found both elements are highly enriched in heavy isotopes

[00:10:06] compared to average solar system values.

[00:10:09] That's due to the loss of lighter isotopes from the upper atmosphere

[00:10:12] as the materials continuously being recycled between Io's interior and atmosphere.

[00:10:18] The findings indicate that Io is probably lost somewhere between 94 and 99%

[00:10:23] of the sulfur that undergoes this outgassing and recycling process.

[00:10:28] They say that would require that Io must have had its current level of volcanic activity

[00:10:33] for its entire existence.

[00:10:35] This is space-time.

[00:10:37] Still to come, Eclipse Project shedding new light on the solar corona.

[00:10:42] And a new study is found that nearly half of China's major coastal cities are sinking.

[00:10:48] All that and more still to come on space-time.

[00:10:52] Scientists around the globe are continuing to sift through the data

[00:11:10] collected from the solar eclipse which spread across North America in early April.

[00:11:14] The breathtaking display came just as the sun was nearing the peak of its 11-year solar cycle.

[00:11:20] The eclipse made landfall on the Mexican Pacific coast

[00:11:24] before arcing up through the southwest, midwest and New England regions of the United States

[00:11:28] then across eastern Canada before finally heading out into the Atlantic Ocean near Newfoundland.

[00:11:34] As well as more than 40 citizen science projects, NASA launched a small amater of rockets,

[00:11:39] jets and drones to monitor the spectacle in great detail.

[00:11:43] These included three BlackBrandt 9 sounding rockets from the Wallops Island Flight Facility

[00:11:49] on the Virginia-Medalantic coast, a specially equipped drone from Fort Drum in New York State

[00:11:54] and NASA's high altitude WB 57 jet.

[00:11:58] The Southwest Research Institute executed two experiments by land and air

[00:12:03] collecting unique solar data from the eclipse.

[00:12:06] There was CATE, its Citizen Continental America Telescope Eclipse Project

[00:12:11] which engaged more than 200 citizen scientists to make a continuous 60-minute high-resolution movie of the eclipse.

[00:12:19] A nearly simultaneous investigation used unique equipment installed on NASA's WB 57 high altitude jet

[00:12:26] which chased the eclipse shadow across America making observations of the sun's outer atmosphere corona

[00:12:32] which were only accessible using a high altitude aircraft.

[00:12:35] Total solar eclipses offer unique opportunities for scientists to study the hot atmosphere above the sun's visible surface.

[00:12:42] They allow scientists to view complex and dynamic features of the sun's outer atmosphere

[00:12:47] in ways that simply aren't possible or practical by any other means

[00:12:51] thereby they open new windows into science's understanding of the solar corona.

[00:12:56] And we just can't do these without an eclipse because the light from the corona is usually overpowered

[00:13:01] by the intense glare of the sun itself and some wavelengths of light are also blocked out by its atmosphere.

[00:13:07] Luckily the WB 57 can fly high enough to be above most of the atmosphere.

[00:13:12] Now while NASA's jet was flying high up in the sky,

[00:13:15] the CATE project deployed a network of 35 teams of citizen scientists

[00:13:19] representing local communities along the eclipse path, the so-called line of totality.

[00:13:24] They deployed a small bucket brigade of small telescopes following the eclipse path across the country.

[00:13:30] Their scientific objectives required measuring the polarization of light

[00:13:34] or the orientation of oscillating light waves in the corona.

[00:13:38] Their telescopes were fitted with special polarizing filters

[00:13:41] baked onto every pixel of the sensor, allowing scientists to measure four different angles of polarization in the corona.

[00:13:48] Meanwhile the airborne project to observe the corona during the eclipse from 50,000 feet above the WB 57

[00:13:54] provided measurements that can't be made from the ground

[00:13:57] using a new suite of sensitive high-speed visible light infrared images.

[00:14:01] These were built by NASA's Langley Research Center and installed in the jet's nose cone.

[00:14:06] Looking at complex motions in the solar corona at new wavelengths and with new polarization measurements

[00:14:12] will help scientists better understand why it's so hot.

[00:14:15] The corona is millions of degrees Celsius

[00:14:18] and that's hundreds of times hotter than the visible surface below.

[00:14:22] A curious paradox that's long intrigued the scientific community.

[00:14:26] The solar corona is also one of the major sources of eruptions which cause geomagnetic storms on Earth.

[00:14:32] These can damage satellites, cause power blackouts and disrupt communications and navigation systems.

[00:14:38] So it's important to understand it better as the world becomes increasingly dependent on these systems.

[00:14:44] Dan Seton who led both projects for the Southwest Research Institute

[00:14:48] says combining the airborne mobile data with the Cade observations

[00:14:52] provides a more complete picture of the sun's mysterious corona.

[00:14:56] Co-researcher Amy Caspi says both experiments required an enormous effort and precise timing

[00:15:02] to get the data they needed.

[00:15:04] The odds of seeing an eclipse in your human lifetime if you can't fly to one,

[00:15:09] if you can't travel to one is actually quite small.

[00:15:12] We here at Southwest Research Institute are leading two exciting eclipse projects to chase the eclipse.

[00:15:18] One of them chasing it in the air literally using NASA's WB-57 high altitude jets

[00:15:24] outfitted with telescopes in the nose cones fly at 50,000 feet, chase the eclipse at about 400 knots or 460 miles an hour.

[00:15:33] The second project is having the eclipse chase us.

[00:15:36] So we deploy 35 teams of community participants or citizen scientists as they sometimes are called

[00:15:43] all the way along the eclipse path from Texas to Maine.

[00:15:47] Each team is getting a telescope, a camera, a mount and other equipment and training so that they can observe the eclipse as it passes overhead

[00:15:56] and it'll be like a bucket brigade where each team sees the shadow right before the next team does

[00:16:02] so that together when we put all of the data together we can get over an hour of totality

[00:16:07] which is something that will allow us to study the corona.

[00:16:11] There's still a lot of open questions about the sun.

[00:16:14] One of them is why the corona is so hot.

[00:16:17] The surface of the star that we can see is about 6000 degrees Kelvin or about 10,000 degrees Fahrenheit

[00:16:24] but the corona is millions of degrees.

[00:16:27] It's like being next to a campfire and the further away you get from the campfire the hotter it gets.

[00:16:33] It's counter-intuitive. It's not something that we're used to thinking about.

[00:16:37] So by observing the solar corona during a total eclipse with high resolution and high speed

[00:16:44] and polarized light like we're doing with our community participants in the CATE 2024 experiment

[00:16:50] we're going to learn a lot of new information that will help us dig into these mysteries.

[00:16:54] That's Amir Kaspe from the Southwest Research Institute

[00:17:06] and this is Space Time

[00:17:24] and time that I take another brief look at some of the other stories making news in Science this week

[00:17:28] with the Science Report.

[00:17:31] A new study shows that if you don't get as much sleep as you really need, a so-called short sleeper

[00:17:36] you could be at a higher risk of type 2 diabetes even if you're a health eater.

[00:17:41] The findings reported in the Journal of the American Medical Association

[00:17:44] are based on data from 247,867 adults in the UK

[00:17:50] finding that people sleeping less than 6 hours daily had a notably higher risk of developing type 2 diabetes

[00:17:55] compared to those who slept 7 or 8 hours.

[00:17:59] The authors also found that this increased risk was seen even in people with healthy diets

[00:18:04] despite this factor usually reducing type 2 diabetes risk.

[00:18:08] Now while this kind of study can't show cause and effect

[00:18:11] the findings do show the importance of sleeping well and eating well

[00:18:14] especially for those at higher risk of developing diabetes.

[00:18:19] A new study has found that nearly half of China's major cities are sinking.

[00:18:24] The findings reported in the Journal Nature also show that a quarter of China's coastal land

[00:18:29] is expected to slip below sea level in coming decades.

[00:18:33] The lands subsidence will affect hundreds of millions of people.

[00:18:37] Researchers say a range of natural and human factors are to blame

[00:18:41] including the depth of a city's bedrock, groundwater depletion, the weight of buildings

[00:18:46] and even the use of transport systems and underground mining.

[00:18:50] A new study shows that older adults with attention deficit hyperactivity disorder

[00:18:55] are more likely to be in a car crash, receive a traffic fine

[00:18:59] or have to break aggressively to avoid a collision.

[00:19:02] The findings reported in the Journal of the American Medical Association

[00:19:05] looked at data from 2,832 drivers aged between 65 and 79.

[00:19:12] Researchers collected data on hard breaking events, self-reported traffic fines

[00:19:16] and vehicle accidents over an average of 3.5 years.

[00:19:20] They found self-reported ADHD was associated with a 7% increased risk of hard breaking events

[00:19:26] a 102 increased risk of receiving a fine

[00:19:29] and a 74% increased risk of being involved in a crash.

[00:19:33] The new findings are important as most research interdrivers with ADHD

[00:19:38] has always focused on younger people.

[00:19:41] And time now for what's got to be the silliest story of the week, maybe even the year.

[00:19:47] A part-time singer who claims she was stalked by a ghost

[00:19:50] but later decided she liked it and apparently married the manifestation

[00:19:54] has now divorced him.

[00:19:56] Err, it. The entity anyway.

[00:19:59] I don't know what the correct pronouns are for this sort of thing.

[00:20:01] Now that divorce came about because apparently this philandering fat

[00:20:05] woman was unfaithful to her.

[00:20:07] Tim Mendham from Australia's Skeptic says

[00:20:09] she's now starting a new career as a paranormal investigator.

[00:20:13] Well of course she is.

[00:20:15] This is a story where you start off with a deep sigh.

[00:20:18] It is one of the good ones but this is what we call the silly story of the week.

[00:20:21] This was a woman in the UK who's a singer

[00:20:24] who claimed that she was assaulted really by a ghost a few years ago

[00:20:28] and they got to like each other a bit.

[00:20:31] They got married, this real woman and this ghost got married.

[00:20:34] But then she got a bit upset because the ghost's interest started wandering

[00:20:38] and apparently he had the hots or the colds or whatever from Marilyn Monroe.

[00:20:43] So he was being sort of a bit unfaithful to her in the ghost realm.

[00:20:47] She could see right through him.

[00:20:49] They had her falling out. They got divorced.

[00:20:51] I'm not sure where they got married and where they got divorced.

[00:20:53] Which particular court or sort of place where you can marry a ghost

[00:20:58] and little end divorce ago.

[00:21:00] She's now setting herself up as a paranormal investigator

[00:21:04] and apparently this ghost is the ghost of this Victorian era soldier named Eduardo.

[00:21:09] Doesn't sound really Victorian era but never mind.

[00:21:11] He's now looking sublimely upon her and smiling at her and saying yes we are.

[00:21:15] He's all settled down there.

[00:21:16] We've got over our divorce.

[00:21:17] Now Missy's sort of unfaithfulness

[00:21:19] and he is now giving her his blessing

[00:21:22] and she's carrying on as a paranormal investigator.

[00:21:25] Talking with other ghosts.

[00:21:27] But apparently he's not very upset with that.

[00:21:29] The interesting thing is that she had this story a while ago being married

[00:21:32] to this fellow and now she's got this divorce story

[00:21:35] and it tends to come out the same time as she's a singer

[00:21:37] and she's got an album coming.

[00:21:39] I wonder, I can't impugn her motive.

[00:21:42] I don't know. Maybe she seriously believes this stuff

[00:21:44] but it also ties in very well with a bit of self promotion

[00:21:47] for whatever reason.

[00:21:48] Apparently she has followers.

[00:21:49] When we were talking about this last time a couple of months ago

[00:21:52] you were questioning what the quality of the album was likely to be like

[00:21:55] if she needs this sort of promotion.

[00:21:57] Yes, I know.

[00:21:58] I haven't heard the music. I don't know.

[00:22:00] I must have got no idea whether it's sort of ethereal music

[00:22:03] or whether it's heavy metal or what.

[00:22:05] This is produced, married, divorced, now blessed

[00:22:08] and the source of a whole new career for this person.

[00:22:10] So I don't believe it personally.

[00:22:12] That's Tim Endham from Australian Skeptics

[00:22:15] and that's the show for now.

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