Science
Earth’s innermost layer is a 400-mile-wide ball of iron, new study suggests
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Scientists have long wondered what lies at the very center of the Earth, and the latest research is putting weight behind a theory that our planet has a distinct ball of iron within its metallic core.
Beneath the outermost crust, the mantle and the molten-liquid outer core lies the Earth’s solid metal center — which actually has a hidden layer, or an “innermost inner core” within, according to a new study published Tuesday in the journal Nature Communications.
The rotation of Earth’s core may have paused, scientists in China have suggested.
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The monumental finding suggests the Earth has five major layers instead of four, and offered new details scientists could use to help unlock some of the oldest mysteries about our planet and how it was formed.
Geoscientists first suggested that the Earth’s core might have an additional, imperceptible layer about 20 years ago, according to a news release. Now, using new data sets collected by measuring the seismic waves of earthquakes as they passed through the Earth’s center, researchers have finally detected that innermost core, the new study said.
Seismic waves are vibrations that run within or along the surface of the Earth and through its inner layers as a result of earthquakes, volcanoes or other means.
“In this study, for the first time, we report observations of seismic waves originating from powerful earthquakes traveling back and forth from one side of the globe to the other up to five times like a ricochet,” study coauthor Dr. Thanh-Son Phạm, a seismologist and postdoctoral fellow at the Research School of Earth Sciences at the Australian National University in Canberra, in an email.
Detection through quake activity
The reason this layer had not been previously observed in more detail is because its composition is so similar to what lies above it, Pham said. Both this newly detected center — which the study reports is likely a 400-mile-wide (644-kilometer-wide) ball of metal — and its outer shell are made of iron-nickel alloy, with trace amounts of other elements.
“Additionally, the transition from the innermost (solid) ball to the outer shell of the inner core (also solid shell) seems rather gradational than sharp,” Pham said. “That is why we cannot observe it via direct reflections of seismic waves from it.”
Using instruments that detect the vibrational waves, researchers found the innermost inner core has a distinct anisotropy, which is a property of a substance that allows it to take on different characteristics depending on the angle from which it’s approached. An example of an object that’s anisotropic is a piece of wood: It’s much easier to hack a piece of firewood apart by hitting it along the direction of its grain than against it.
It is that feature that distinguishes the innermost core.
When it came to assessing the Earth’s core, researchers looked at how fast seismic waves traveled through it in different directions, and they found the innermost inner core changed the speed of those waves in a different way than the layer above it, the center core’s outer shell.
Detecting the new layer more than 1,000 miles (1,600 kilometers) beneath our feet is significant. The presence of a distinct innermost core could give scientists a better understanding of Earth’s magnetic field and how it has evolved and will continue to do so.
The new finding also “gives us a glimpse of what might have happened with other planets,” Pham said. “Take Mars as an example. We don’t understand yet why (Mars’ magnetic field) ceased to exist in the past.”
This visualization shows water features on New York’s Long Island – shown as bright pink splotches. Purple, yellow, green, and dark blue shades represent different land elevations, while the surrounding ocean is a lighter blue. The data was collected on Jan. 21, 2023, by SWOT’s KaRIn instrument. Credit: NASA/JPL-Caltech
The Surface Water and Ocean Topography mission offers the first taste of the detailed perspectives of Earth’s surface water that its cutting-edge instruments will be able to capture.
The international Surface Water and Ocean Topography (SWOT) mission – led by NASA and the French space agency Centre National d’Études Spatiales (CNES) – has sent back some of its first glimpses of water on the planet’s surface, showing ocean currents like the Gulf Stream in unprecedented detail. SWOT is also capturing views of freshwater features such as lakes, rivers, and other water bodies down to about 300 feet (100 meters) wide.
The satellite will measure the elevation of nearly all the water on Earth’s surface and provide one of the most comprehensive surveys yet of our planet’s surface water. SWOT’s measurements of freshwater bodies and the ocean will provide insights into how the ocean influences climate change and the water cycle; how a warming world affects water storage in lakes, rivers, and reservoirs; and how communities can better manage their water resources and prepare for floods and other disasters.
“SWOT’s advanced imagery will empower researchers and advance the way we manage fresh water and the effects of sea level rise across the globe,” said NASA Administrator Bill Nelson. “Water is one of our planet’s most important resources – and it’s proven to be vulnerable to the impacts of climate change. SWOT will provide critical information that communities can use to prepare for the impacts of a warming climate.”
A Whole New View
As seen in these early images, on Jan. 21, 2023, SWOT measured sea level in a part of the Gulf Stream off the coast of North Carolina and Virginia. The two antennas of SWOT’s Ka-band Radar Interferometer (KaRIn) instrument acquired data that was mapped as a pair of wide, colored strips spanning a total of 75 miles (120 kilometers) across. Red and orange areas in the images represent sea levels that are higher than the global average, while the shades of blue represent sea levels that are lower than average.
For comparison, the new data is shown alongside sea surface height data taken by space-based instruments called altimeters. The instruments – widely used to measure sea level – also bounce radar signals off of Earth’s surface to collect their measurements. But traditional altimeters are able to look only at a narrow beam of Earth directly beneath them, unlike KaRIn’s two wide-swath strips that observe sea level as a two-dimensional map.
The spatial resolution of SWOT ocean measurements is 10 times greater than the composite of sea surface height data gathered over the same area by seven other satellites: Sentinel-6 Michael Freilich, Jason-3, Sentinel-3A and 3B, Cryosat-2, Altika, and Hai Yang 2B. The composite image was created using information from the Copernicus Marine Service of ESA (European Space Agency) and shows the same day as the SWOT data.
KaRIn also measured the elevation of water features on Long Island – shown as bright pink splotches nestled within the landscape. (Purple, yellow, green, and blue shades represent different land elevations.)
“Our ability to measure freshwater resources on a global scale through satellite data is of prime importance as we seek to adjust to a changing climate,” said CNES Chairman and CEO Philippe Baptiste. “In this respect, the first views from SWOT give us a clearer picture than ever before. These data will prove highly valuable for the international scientific community in the fields of hydrology, oceanography, and coastal studies.”
This initial inland image is a tantalizing indication of how SWOT can measure details of smaller lakes, ponds, and rivers in ways that satellites could not before. Such data will be used to produce an extraordinary accounting of the freshwater on Earth’s surface in ways useful to researchers, policymakers, and water resource managers.
“The KaRIn instrument took years to develop and build, and it will collect information on bodies of water across the globe – data that will be freely and openly available to everybody who needs it,” said Parag Vaze, SWOT project manager at NASA’s Jet Propulsion Laboratory in Southern California.
More About the Mission
Launched on Dec. 16, 2022, from Vandenberg Space Force Base in central California, SWOT is now in a period of commissioning, calibration, and validation. Engineers are checking out the performance of the satellite’s systems and science instruments before the planned start of science operations in summer 2023.
The data for these first images was collected by SWOT’s KaRIn instrument, the scientific heart of the satellite. KaRIn has one antenna at each end of a boom that’s 33 feet (10 meters) long. This enables the instrument to look off to either side of a center line directly below the satellite as it bounces microwave signals off Earth’s surface. The returning radar signals arrive at each antenna slightly out of sync, or phase, from one another. When these signals are combined with other information about the antennas and the satellite’s altitude, scientists will be able to map the height of water on Earth’s surface with never-before-seen clarity. KaRIn encountered an issue earlier this year with one of its subsystems; engineers have now resolved the situation, and the instrument is up and running.
SWOT was jointly developed by NASA and CNES, with contributions from the Canadian Space Agency (CSA) and the UK Space Agency. JPL, which is managed for NASA by Caltech in Pasadena, California, leads the U.S. component of the project. For the flight system payload, NASA provided the KaRIn instrument, a GPS science receiver, a laser retroreflector, a two-beam microwave radiometer, and NASA instrument operations. CNES provided the Doppler Orbitography and Radioposition Integrated by Satellite (DORIS) system, the dual frequency Poseidon altimeter (developed by Thales Alenia Space), the KaRIn radio-frequency subsystem (together with Thales Alenia Space and with support from the UK Space Agency), the satellite platform, and ground operations. CSA provided the KaRIn high-power transmitter assembly. NASA provided the launch vehicle and the agency’s Launch Services Program, based at Kennedy Space Center, managed the associated launch services.
To learn more about SWOT, visit: https://swot.jpl.nasa.gov/
The Earth witnessed a powerful solar storm in nearly six years, causing auroras all over the US, the National Oceanic and Atmospheric Administration (NOAA) said. NOAA had earlier announced moderate G2 storm and G3 conditions between March 23 and 25, but updated it to G4. A severe G4 storm can affect the power grid system with possible widespread voltage control problems; and spacecraft operations with increased possibility of surface charging, and atmospheric drag risk on Low Earth Orbiting (LEO) satellites.
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Five of the sun’s eight major planets will be lined up on the western horizon this Tuesday just after sunset.
The astronomical delight will comprise Mercury, Venus, Mars, Jupiter and Uranus — all in a visible line from the horizon to the crescent moon.
NASA astronomer Bill Cooke says the best way to get a glimpse is to stand somewhere with a clear view of the western horizon.
The planets will stretch from the horizon to halfway up the night sky.
Mercury and Jupiter (the first and fifth planets from the sun) will dip below the horizon around 30 minutes after sunset, that is 7:37 p.m. on Tuesday.
The five-planet spread can be seen anywhere on Earth.
Venus, Mars and Jupiter will be the brightest, particularly Venus, and Mars will be closest to the moon. Mercury and Uranus will be the dimmest, so a set of binoculars will be useful.
Uranus is the rarest seen of the planetary lineup.
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