Astro Blog

By Hannah Richter , Science.  Excerpt: “Dust is the building block of the universe,” says Melissa Shahbandeh, an astrophysicist at the Space Telescope Science Institute (STScI). Over millions of years, specks of cosmic dust and gas clump together to form large, dense clouds from which planets and stars are born. But the dust’s own origins have been mysterious. Now, in data from NASA’s JWST space observatory, Shahbandeh and her colleagues  have found a source for the dust that filled the early universe : giant stellar explosions called interacting supernovae, whose intense shockwaves can blast out dusty plumes that accumulated in the supernovae’s surroundings. These results, presented last week at the meeting of the American Astronomical Society and submitted to The Astrophysical Journal are “impressive,” says Lifan Wang, an astrophysicist at Texas A&M University who was not involved in the work. ...The findings...deepen understanding of where Earth and everything...

Source:   By Raluca Rufu, Oded Aharonson, & Hagai B. Perets, published in Nature Abstract: The hypothesis of lunar origin by a single giant impact can explain some aspects of the Earth–Moon system. However, it is difficult to reconcile giant-impact models with the compositional similarity of the Earth and Moon without violating angular momentum constraints. Furthermore, successful giant-impact scenarios require very specific conditions such that they have a low probability of occurring. Here we present numerical simulations suggesting that the Moon could instead be the product of a succession of a variety of smaller collisions. In this scenario, each collision forms a debris disk around the proto-Earth that then accretes to form a moonlet. The moonlets tidally advance outward, and may coalesce to form the Moon. We find that sub-lunar moonlets are a common result of impacts expected onto the proto-Earth in the early Solar System and find that the planetary rotati...

Source:   By Catherine Minnehan , EOS—publication of AGU Excerpts: Scientists find a solution to a 200-year-old problem: syncing the prominent bulges on the Moon with our natural satellite's origins. Scientists have known for hundreds of years that the Moon’s rotational and tidal bulges are much larger than expected. The deformation is thought to be a remnant from when the Moon orbited much closer to Earth than it does today. The problem is, the bulges we see require an unusual eccentric orbit—one that scientists do not think the Moon ever had. Keane and Matsuyama solved this problem by discovering a new component to the Moon’s global figure. The Moon is not perfectly spherical because strong forces pull it in different directions. There are two main forces: bulging at the equator due to lunar rotation and bulging on the nearside and farside due to tidal forces between the Earth and the Moon. The observed lunar deformation is much larger than scientists would exp...

Source:   NASA RELEASE 14-236    Using data from NASA’s Gravity Recovery and Interior Laboratory (GRAIL), mission scientists have solved a lunar mystery almost as old as the moon itself. Early theories suggested the craggy outline of a region of the moon’s surface known as Oceanus Procellarum, or the Ocean of Storms, was caused by an asteroid impact. ... However, mission scientists studying GRAIL data believe they have found evidence the craggy outline of this rectangular region -- roughly 1,600 miles (2,600 kilometers) across -- is actually the result of the formation of ancient rift valleys.  ...rifts are buried beneath dark volcanic plains on the nearside of the moon and have been detected only in the gravity data provided by GRAIL. ...The findings are published online in the journal Nature. Another theory arising from recent data analysis suggests this region formed as a result of churning deep in the interior of the moon that led to a hi...

Source:  Daniel Clery, Science    Excerpt:  Where did the moon come from? For 3 decades, planetary scientists have agreed that ... a body the size of Mars struck Earth a glancing blow that reduced both to rubble. The cloud of debris reformed itself into the modern Earth and moon ..."giant impact" theory neatly explained why the rocks Apollo astronauts brought back from the moon closely resembled rocks on Earth—or so it seemed at first. ...recent computer models show, such a collision wouldn't have scrambled the two bodies together enough to explain the similarity. Meeting last month in London to discuss the problem, scientists agreed that the origin of the moon must have been messier and more complicated than anyone had assumed.... [Hear podcast interview at  http://www.sciencemag.org/content/342/6155/183/suppl/DC1 ] http://www.sciencemag.org/content/342/6155/183

Source:   Sindyan N. Bhanoo, The New York Times Excerpt: Astronomers have long theorized that the Moon was formed when an object the size of Mars slammed into Earth, sending a huge mass of rock into orbit around it. “According to the prevailing model prediction, approximately half of the Moon-forming material should come from the Mars-size impactor,” said Junjun Zhang, an isotope geochemist at the University of Chicago and the study’s first author. But samples of isotopic titanium from the Moon and from Earth now suggest that material from Earth is predominant on the Moon, researchers report in the journal Nature Geoscience. …She and her colleagues used lunar samples gathered by the Apollo missions in the 1960s and ’70s. They compared the isotopic titanium ratio in these samples to that of samples from Earth. The researchers also found that meteorites have a much wider range of isotopic titanium. “That also tells us that the impactor that hit the Earth was very unlikely...

Source:    Amy Shira Teitel, Universe Today Excerpt:  …Since 2006, astronomers have been tracking smaller secondary moons that our own Earth-Moon system captures; these metre-wide moons stay for a few months then leave. But what if the Earth actually had a second permanent moon today? How different would life be?   ... For his two-mooned Earth thought experiment, Comins proposes that our Earth-Moon system formed as it did — he needs the same early conditions that allowed life to form — before capturing a third body. This moon, which I will call Luna, sits halfway between the Earth and the Moon.  …Eventually, the Moon and Luna would collide; like the Moon is now, both moons would be receding from Earth.... www.universetoday.com/92148/what-if-the-earth-had-two-moons/

Source:   Bernard Wood, Physics Today  pg. 40 Excerpt: The solar system began to form 4568 million years ago, from a disk of dust and gas around the young Sun. Within a few million years, Jupiter and Saturn had formed and the terrestrial planets had reached significant fractions of their present size. The processes by which the planets formed are of particular interest at a time when the search for Earth-like planets around other stars occupies considerable attention. Earth-like exoplanets somewhat larger than our own are already detectable, ... The mechanisms of initial growth toward large bodies are poorly understood … some combination of mechanical sticking and eventually gravitational perturbation must have formed many 10-km-sized objects in the first 10^4–10^5 years. ...Although some planetesimals would have been destroyed in collisions, others would have continued to accrete…. www.physicstoday.org/resource/1/phtoad/v64/i12/p40_s1

Source:    Amina Khan, Los Angeles Times Excerpt: The moon may be 200 million years younger than widely believed, according to a new analysis of a rock brought back to Earth in 1972 by Apollo 16 astronauts. Or, if not, the moon may never have had the magma ocean that scientists think covered its surface soon after it formed. …an international team of scientists decided to use sophisticated techniques to better test a sample collected by the Apollo 16 mission … a about 4.36 billion years, which surprised the scientists. "We all looked at one another and laughed," said lead author Lars Borg, a geochemist …. If that is correct, it means the moon's magma ocean formed — and cooled — more recently than scientists have generally thought …. This also could mean that the great impact that separated the moon from Earth happened more recently too. www.latimes.com/news/science/la-sci-moon-age-20110818,0,4380476.story

Source:    NASA RELEASE: 11-199 Excerpt:  Analysis of samples returned by NASA's Genesis mission indicates our sun and its inner planets may have formed differently than scientists previously thought. "…findings show that all solar system objects, including the terrestrial planets, meteorites and comets, are anomalous compared to the initial composition of the nebula from which the solar system formed," said Bernard Marty, a Genesis co-investigator from Centre de Recherches Petrographiques et Geochimiques in Nancy, France and the lead author of the second new Science paper. "Understanding the cause of such a heterogeneity will impact our view on the formation of the solar system." For more information on the Genesis mission, visit: genesismission.jpl.nasa.gov www.nasa.gov/home/hqnews/2011/jun/HQ_11-199_Genesis.html

Source:    Nicolas Dauphas and Ali Pourmand, National Science Foundation Excerpt: Mars developed in as little as two to four million years after the birth of the solar system, far more quickly than Earth, according to results of a new study published in this week's issue of the journal Nature. The red planet's rapid formation helps explain why it is so small, say the study's co-authors. www.nsf.gov/news/news_summ.jsp