A close-up of Arrokoth reveals how planetary building blocks were constructed
by Staff Writers
Washington DC (SPX) Feb 14, 2020
The farthest, most primitive object in the Solar System ever to be visited by a spacecraft - a bi-lobed Kuiper Belt Object known as Arrokoth - is described in detail in three new reports. The reports expand upon the first published results on this object, announced in a May 2019 issue of Science, and which were based on just a small amount of data downlinked from the New Horizons spacecraft after the flyby.
The new reports are based on over ten times as much data from the flyby. Together, they provide a far more complete picture of the composition and origin of Arrokoth, and point to the resolution of a longstanding scientific controversy about how such primitive planetary building blocks called planetesimals were formed.
In the first study based on these results, William McKinnon and colleagues used simulations to better understand how Arrokoth formed. Their analysis indicates that the two lobes were previously independent bodies formed close together that assembled into the present-day object very gently.
The finding points to formation in a local collapse cloud of the solar nebula, and not by the other longstanding theory of planetesimal formation, called hierarchical accretion, in which objects from disparate parts of the nebula collided to form the object.
In another study based on these new results, John Spencer and colleagues report that Arrokoth's binary lobes are less flat than initially inferred and have larger volumes than previous estimates suggested.
Spencer and colleagues further report that Arrokoth has a smooth, lightly cratered surface, different from that of previously visited solar system bodies, indicating its face has mostly remained well-preserved since the end of the planet formation era. From the crater density, they infer an ancient age of its surface of about 4 billion years, supporting the discovery that Arrokoth was formed in a local solar nebula collapse cloud.
Finally, Will Grundy and colleagues investigate the composition, color and temperature of Arrokoth's surface and find it to be uniformly red, cold, and covered with methanol ice and unidentified complex organic molecules.
The red color is likely due to the presence of organic molecules. Grundy et al. also offer several suggestions as to how methanol could have formed on this object, including formation by cosmic ray irradiation of mixed water and methane ices.
Although water was not detected on Arrokoth, it could be present, the authors say, but somehow masked or hidden from view. The uniform color and composition of Arrokoth's surface also support the discovery that Arrokoth was formed in a local solar nebula collapse cloud. The significance of the three studies is further discussed in a related Perspective.
Why Uranus and Neptune are different
Bern, Switzerland (SPX) Feb 05, 2020
Uranus and Neptune are the outermost planets of the solar system. In size, possibly bulk composition, and their large distance from the Sun they are similar and clearly segregated from the inner terrestrial planets and the gas giants Jupiter and Saturn. "However, there are also striking differences between the two planets that require explanation," says Christian Reinhardt, who studied Uranus and Neptune together with Alice Chau, Joachim Stadel and Ravit Helled, all PlanetS members working at the ... read more
|The content herein, unless otherwise known to be public domain, are Copyright 1995-2024 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. All articles labeled "by Staff Writers" include reports supplied to Space Media Network by industry news wires, PR agencies, corporate press officers and the like. Such articles are individually curated and edited by Space Media Network staff on the basis of the report's information value to our industry and professional readership. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. General Data Protection Regulation (GDPR) Statement Our advertisers use various cookies and the like to deliver the best ad banner available at one time. All network advertising suppliers have GDPR policies (Legitimate Interest) that conform with EU regulations for data collection. By using our websites you consent to cookie based advertising. If you do not agree with this then you must stop using the websites from May 25, 2018. Privacy Statement. Additional information can be found here at About Us.