Peta Baharu Asteroid Psyche yang Luar Biasa Mendedahkan Dunia Logam dan Batu Purba

Ahli astronomi di MIT dan tempat lain telah memetakan komposisi asteroid Psyche, mendedahkan permukaan logam, pasir dan batu. Kredit: Tangkapan skrin ihsan NASA

Permukaan asteroid Psyche yang berbeza-beza mencadangkan sejarah dinamik, yang boleh termasuk letusan logam, kesan gegaran asteroid dan mantel berbatu yang hilang.

Akhir tahun ini,[{” attribute=””>NASA is set to launch a probe the size of a tennis court to the asteroid belt, a region between the orbits of Mars and Jupiter where remnants of the early solar system orbit the sun. Once within the asteroid belt, the spacecraft will zero in on Psyche, a large, metal-rich asteroid that is thought to be the ancient core of an early planet. The probe, named after its asteroid target, will then spend close to two years orbiting and analyzing Psyche’s surface for clues to how early planetary bodies evolved.

Ahead of the mission, which is led by principal investigator Lindy Elkins-Tanton ’87, SM ’87, PhD ’02, planetary scientists at MIT and elsewhere have now provided a sneak peek of what the Psyche spacecraft might see when it reaches its destination.

In a paper published on June 15, 2022, in the Journal of Geophysical Research: Planets, the planetary science team presents the most detailed maps of the asteroid’s surface properties to date, based on observations taken by a large array of ground telescopes in northern Chile. The maps reveal vast metal-rich regions sweeping across the asteroid’s surface, along with a large depression that appears to have a different surface texture between the interior and its rim; this difference could reflect a crater filled with finer sand and rimmed with rockier materials.

Psyche Spacecraft at the Asteroid Psyche (Illustration)

This illustration, updated in April 2022, depicts NASA’s Psyche spacecraft. Set to launch in August 2022, the Psyche mission will explore a metal-rich asteroid of the same name that lies in the main asteroid belt between Mars and Jupiter. The spacecraft will arrive in early 2026 and orbit the asteroid – also shown in this illustration – for nearly two years to investigate its composition. Credit: NASA/JPL-Caltech/ASU

Overall, Psyche’s surface was found to be surprisingly varied in its properties.

The new maps hint at the asteroid’s history. Its rocky regions could be vestiges of an ancient mantle — similar in composition to the rocky outermost layer of Earth, Mars, and the asteroid Vesta — or the imprint of past impacts by space rocks. Finally, craters that contain metallic material support the idea proposed by previous studies that the asteroid may have experienced early eruptions of metallic lava as its ancient core cooled.

“Psyche’s surface is very heterogeneous,” says lead author Saverio Cambioni, the Crosby Distinguished Postdoctoral Fellow in MIT’s Department of Earth, Atmospheric and Planetary Sciences (EAPS). “It’s an evolved surface, and these maps confirm that metal-rich asteroids are interesting, enigmatic worlds. It’s another reason to look forward to the Psyche mission going to the asteroid.”

Cambioni’s co-authors are Katherine de Kleer, assistant professor of planetary science and astronomy at Caltech, and Michael Shepard, professor of environmental, geographical, and geological sciences at Bloomsburg University.

Telescope Power

The surface of Psyche has been a focus of numerous previous mapping efforts. Researchers have observed the asteroid using various telescopes to measure light emitted from the asteroid at infrared wavelengths, which carry information about Psyche’s surface composition. However, these studies could not spatially resolve variations in composition over the surface.

Cambioni and his colleagues instead were able to see Psyche in finer detail, at a resolution of about 20 miles per pixel, using the combined power of the 66 radio antennas of the Atacama Large Millimeter/submillimeter Array (ALMA) in northern Chile. Each antenna of ALMA measures light emitted from an object at millimeter wavelengths, within a range that is sensitive to temperature and certain electrical properties of surface materials.

“The signals of the ALMA antennas can be combined into a synthetic signal that’s equivalent to a telescope with a diameter of 16 kilometers (10 miles),” de Kleer says. “The larger the telescope, the higher the resolution.”

On June 19, 2019, ALMA focused its entire array on Psyche as it orbited and rotated within the asteroid belt. De Kleer collected data during this period and converted it into a map of thermal emissions across the asteroid’s surface, which the team reported in a 2021 study. Those same data were used by Shepard to produce the most recent high-resolution 3D shape model of Psyche, also published in 2021.


Di sebelah kiri, peta ini menunjukkan sifat permukaan pada Psyche, daripada kawasan berpasir (ungu/rendah) kepada kawasan berbatu (kuning/tinggi). Peta di sebelah kanan menunjukkan banyak logam pada Psyche, daripada rendah (ungu) kepada tinggi (kuning).

Untuk menangkap perlawanan

Dalam kajian baharu, Cambioni menjalankan simulasi Psyche untuk melihat sifat permukaan yang paling sesuai dan menerangkan pelepasan haba yang diukur. Dalam setiap ratusan senario simulasi, dia menetapkan permukaan asteroid dengan kombinasi bahan yang berbeza, seperti kawasan yang mempunyai banyak logam yang berbeza. Dia memodelkan putaran asteroid dan mengukur bagaimana bahan simulasi pada asteroid akan mengeluarkan pelepasan haba. Cambioni kemudian mencari pelepasan simulasi yang paling sepadan dengan pelepasan sebenar yang diukur oleh ALMA. Senario itu, katanya, akan mendedahkan peta paling mungkin bagi bahan permukaan asteroid itu.

“Kami menjalankan simulasi ini kawasan mengikut kawasan supaya kami dapat menangkap perbezaan dalam sifat permukaan,” kata Cambioni.

Kajian itu menghasilkan peta terperinci sifat permukaan Psyche, menunjukkan bahawa muka depan asteroid berkemungkinan diliputi dalam kepelbagaian bahan yang besar. Para penyelidik mengesahkan bahawa, secara keseluruhan, permukaan Psyche kaya dengan logam, tetapi banyaknya logam dan silikat berbeza-beza di seluruh permukaannya. Ini mungkin petunjuk lanjut bahawa, pada awal pembentukannya, asteroid itu mungkin mempunyai mantel yang kaya dengan silikat yang telah hilang.

Mereka juga mendapati bahawa, semasa asteroid berputar, bahan di bahagian bawah lekukan besar – kemungkinan kawah – berubah suhu lebih cepat daripada bahan di sepanjang rim. Ini menunjukkan bahawa bahagian bawah kawah diliputi dalam “kolam” bahan berbutir halus, seperti pasir di Bumi, yang menjadi panas dengan cepat, manakala rim kawah terdiri daripada bahan yang lebih berbatu, lebih perlahan kepada panas.

“Kolam bahan berbutir halus telah dilihat pada asteroid kecil, yang gravitinya cukup rendah untuk kesan menggoncang permukaan dan menyebabkan bahan yang lebih halus berkumpul,” kata Cambioni. “Tetapi Psyche adalah badan yang besar, jadi jika bahan berbutir halus terkumpul di bahagian bawah kemurungan, ini menarik dan agak misteri.”

“Data ini menunjukkan bahawa permukaan Psyche adalah heterogen, dengan kemungkinan variasi yang luar biasa dalam komposisi,” kata Simone Marchi, saintis kakitangan di Institut Penyelidikan Barat Daya dan penyiasat bersama misi Psyche NASA, yang tidak terlibat dalam kajian semasa. “Salah satu matlamat utama misi Psyche adalah untuk mengkaji komposisi permukaan asteroid menggunakan sinar gamma dan spektrometer neutron dan pengimejan warna. Jadi, kemungkinan kehadiran heterogeniti komposisi adalah sesuatu yang Pasukan Sains Jiwa tidak sabar-sabar untuk mengkaji lebih banyak lagi.”

Rujukan: “The Heterogenous Surface of Asteroid (16) Psyche” oleh Saverio Cambioni, Katherine de Kleer dan Michael Shepard, 19 Mei 2022, Jurnal Penyelidikan Geofizik: Planet.
DOI: 10.1029/2021JE007091

Penyelidikan ini disokong oleh EAPS Crosby Distinguished Postodoctoral Fellowship, dan sebahagiannya oleh Yayasan Heising-Simons.

We wish to thank the writer of this post for this outstanding content

Peta Baharu Asteroid Psyche yang Luar Biasa Mendedahkan Dunia Logam dan Batu Purba


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