2023-08-27 16:07:24
French novelist Jules Verne delighted 19th-century readers with the seductive idea that a trip to the center of the Earth was in fact plausible.
But scientists have long recognized that Verne’s book was science fiction. The extreme temperatures inside the Earth – around 5,537 Celsius at the core – and the accompanying crushing pressure, which is millions of times greater than on the surface, prevent humans from venturing there.
We still know a certain number of things regarding the interior of the Earth. For example, geophysicists have discovered that the core consists of a solid sphere of iron and nickel that is 20% of the Earth’s radius, surrounded by a shell of molten iron and nickel that spans 15 additional % of Earth’s radius.
This information, along with the rest of our knowledge regarding the interior of our world, was acquired indirectly – either by studying the Earth’s magnetic field or by studying how seismic waves bounce off different layers beneath the Earth’s surface. .
But indirect discovery has its limits. How can scientists learn more regarding the depths of our planet?
Planetary scientists like me think the best way to learn regarding the Earth’s interior is to go to space. via the liftoff of NASA’s robotic mission to a metallic world which is scheduled for October 5, 2023. This mission, the spacecraft that will go there and the world it will explore all have the same name: Psyche (Psyché in French). And for six years now, I’ve been part of NASA’s Psyche team.
A presentation of the Psyché mission with Jim Bell. To obtain a fairly accurate French translation, click on the white rectangle at the bottom right. The English subtitles should then appear. Then click on the nut to the right of the rectangle, then on “Subtitles” and finally on “Translate automatically”. Choose “French”. © Nasa
About the asteroid Psyche
Asteroids are small worlds, some the size of small cities and others as large as small countries. These are the remaining building blocks of the early and violent period of planetary formation in our Solar System.
Although most are rocky, icy, or a combination of the two, perhaps 20% of asteroids are metallic worlds and similar in composition to Earth’s core. So it’s tempting to imagine that these metallic asteroids are pieces of the cores of once-existing planets, torn apart by ancient cosmic collisions with each other. Perhaps by studying these pieces, scientists might directly discover what a planetary core looks like.
Psyche is the largest known metallic asteroid. Discovered in 1852, Psyche is the width of Massachusetts, a crushed spherical shape reminiscent of a pin cushion and orbiting between Mars and Jupiter in the main asteroid belt. An amateur astronomer can see Psyche with a garden telescope, but she only appears as a point of light.
A simulation of Psyche’s flyby. To obtain a fairly accurate French translation, click on the white rectangle at the bottom right. The English subtitles should then appear. Then click on the nut to the right of the rectangle, then on “Subtitles” and finally on “Translate automatically”. Choose “French”. © Nasa
About the Psyche Mission
In early 2017, NASA approved the billion dollar mission to Psyche. To do its job, the unmanned spacecraft will not need to land. It will orbit the asteroid repeatedly and methodically, starting at 700 kilometers and then descending to 75 kilometers from the surface, and possibly even lower.
Once it arrives in August 2029, the probe will spend 26 months mapping the asteroid’s geology, topography and gravity; she will look for evidence of a magnetic field; and it will compare the composition of the asteroid with what scientists know, or think they know, regarding Earth’s core.
The central questions are: Is Psyche really an exposed planetary core? Is the asteroid a large boulder of bedrock, a pile of rubble of small boulders, or something else entirely? Are there any clues that the previous outer layers of this little world – the crust and the mantle – were violently torn away a long time ago? And perhaps the most critical question: can what we learn regarding Psyche be extrapolated to solve some of the mysteries of the Earth’s core?
About the Psyche spacecraft
The probe body is regarding the same size and mass as a large SUV. Solar panels, stretching a little wider than a tennis court, power the cameras, spectrometers and other systems.
A SpaceX Falcon Heavy rocket will blast off Psyche from Earth. For the rest, Psyche will rely on ion propulsion: the gentle pressure of ionized xenon gas spurting out of a nozzle provides a continuous, reliable, and inexpensive way to propel a spacecraft through the Solar System.
The journey, a slow 4 billion kilometer spiral that includes a gravity-assisted flyby past Mars, will take nearly six years. Throughout the cruise, the Psyché team from Jet Propulsion Laboratory from NASA in Pasadena, California, and the team atArizona State University in Tempe, will remain in regular contact with the spacecraft. Our team will send and receive data using the network Deep Space NASA’s giant radio antennae.
Even if we learn that Psyche is not an ancient planetary core, we will certainly add significantly to our body of knowledge regarding the Solar System and how planets form. After all, Psyche is unlike any other world humans have ever visited. We may not yet be able to travel to the center of the Earth, but robotic avatars in places like Psyche can help unravel the mysteries hidden deep within planets, including our own.
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