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Evolution of the P/Shoemaker-Levy 9 "Gang of Four" Region


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This series of eight NASA Hubble Space Telescope "snapshots" shows the evolution of the P-Q complex, also called the "gang of four" region, of comet P/Shoemaker-Levy 9.

The eight individual frames chronicle changes in the comet during the 12 months before colliding with Jupiter. The sequence shows that the relative separations of the various cometary fragments, thought to range in size from about 500 meters to almost 4 km (2.5 miles) across, changed dramatically over this period. The apparent separation of Q1 and Q2 was only about 1100 kilometers (680 miles) on 1 July 1993 and increased to 28,000 kilometers (17,400 miles) by 20 July 1994.

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      Detailed Daily Guide
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      Thursday evening, December 5, the planet Mercury will be passing between the Earth and the Sun as seen from the Earth, called inferior conjunction. Planets that orbit inside of the orbit of Earth can have two types of conjunctions with the Sun, inferior (when passing between the Earth and the Sun) and superior (when passing on the far side of the Sun as seen from the Earth). Mercury will be shifting from the evening sky to the morning sky and will begin emerging from the glow of dawn on the eastern horizon in less than a week.
      Saturday afternoon, December 7, the planet Jupiter will be at its closest and brightest for the year, called “opposition” because it will be opposite the Earth from the Sun, effectively a “full” Jupiter. Jupiter will be 12 degrees above the east-northeastern horizon as evening twilight ends (at 5:49 PM EST), will reach its highest in the sky right around midnight (11:59 PM), and will be 11 degrees above the west-northwestern horizon as morning twilight begins (Sunday morning at 6:11 AM). Only planets that orbit farther from the Sun than the Earth can be seen at opposition.
      Saturday evening, December 7, the planet Saturn will appear to the upper left of the waxing crescent Moon. They will be 6 degrees apart as evening twilight ends (at 5:49 PM EST). Saturn will appear to shift clockwise and closer to the Moon, so that by the time the Moon sets 5.5 hours later (at 11:18 PM) Saturn will be 3.5 degrees above the Moon on the west-southwestern horizon. For a swath in the Pacific Ocean off the coast of Asia the Moon will actually block Saturn from view, see http://lunar-occultations.com/iota/planets/1208saturn.htm for a map and information on the locations that can see this eclipse.
      Sunday morning, December 8, the Moon will appear half-full as it reaches its first quarter at 10:27 AM EST (when we can’t see it).
      Thursday morning, December 12, will be the first morning the planet Mercury will be above the east-southeastern horizon as morning twilight begins (at 6:14 AM EST).
      Thursday morning, December 12, at 8:18 AM EST, the Moon will be at perigee, its closest to the Earth for this orbit.
      Friday evening into Saturday morning, December 13 to 14, the Pleiades star cluster will appear near the full Moon. This may best be viewed with binoculars, as the brightness of the full Moon may make it hard to see the stars in this star cluster. As evening twilight ends (at 5:50 PM EST), the Pleiades will appear 4 degrees to the upper right of the full Moon. By the time the Moon reaches its highest for the night (at 10:49 PM), the Pleiades will be 6 degrees to the right. By about 2 AM the Pleiades will be 8 degrees to the lower right of the Moon and they will continue to separate as the morning progresses.
      As mentioned above, one of the three major meteor showers of the year, the Geminids (004 GEM), will peak Saturday morning, December 14. The light of the nearly full Moon will interfere. In a good year, this shower can produce 150 visible meteors per hour under ideal conditions, but this will not be a good year. For the Washington, DC area the MeteorActive app predicts that at about 2 AM EST on the morning of December 14, under bright suburban sky conditions, the peak rate from the Geminids and all other background sources might reach 20 meteors per hour. See the meteor summary above for suggestions for meteor viewing.
      Saturday morning, December 14, the full Moon, the bright planet Jupiter, and the bright star Aldebaran will form a triangle. As Aldebaran sets on the west-northwestern horizon (at 6:10 AM EST) it will be 9 degrees to the lower left of the Moon with Jupiter 7 degrees to the upper left of the Moon. Morning twilight will begin 6 minutes later.
      Saturday evening, December 15, the full Moon will have shifted to the other side of Jupiter. Jupiter will be 6 degrees to the right of the Moon as evening twilight ends (at 5:50 PM EST) and the pair will separate as the night progresses.  
      The full Moon after next will be Sunday morning, December 15, 2024, at 4:02 AM EST. This will be Saturday evening from Alaska Time westwards to the International Date Line. The Moon will appear full for about 3 days around this time, from Friday evening through Monday morning, making this a full Moon weekend.
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      NASA-supported scientists have examined the long and intricately linked history of microbial life and the Earth’s environment. By reviewing the current state of knowledge across fields like microbiology, molecular biology, and geology, the study looks at how microorganisms have both shaped and been shaped by chemical properties of our planet’s oceans, land, and atmosphere. The study combines data across multiple fields of study and discusses how information on the complicated history of life on our planet from a single field cannot be viewed in isolation.
      An artist interpretation of the hazy atmosphere of Archean Earth – a pale orange dot. NASA’s Goddard Space Flight Center/Francis Reddy The first life on Earth was microbial. Today the vast majority of our planet’s biomass is still made up of tiny, single-celled microorganisms. Although they’re abundant, the history of microbes can be a challenge for astrobiologists to study. Microbes don’t leave bones, shells or other large fossils behind like dinosaurs, fish or other large organisms. Because of this, scientists must look at different evidence to understand the evolution of microbial life through time.
      In order to study ancient microbes on Earth, astrobiologists look for isotopic fingerprints in rocks that can be used to identify the metabolisms of ancient communities. Metabolism refers to the conversion of food into energy, and happens in all living things. Many elements (think carbon (C), nitrogen (N), Sulfur (S), iron (Fe)) are involved in microbial metabolism. As microbes process these elements, they cause isotopic changes that scientists can spot in the rock record. Microbes also help to control how these elements are deposited and cycled in the environment, affecting geology and chemistry at both local and global scales (consider the role of microbes in the carbon cycle on Earth today).
      This photograph shows a section of the Marble Bar formation in the Pilbara region of north-western Western Australia. The bands of color in the rock are the result of high amounts of certain minerals, including iron, that may have resulted from microbial activity on the ancient Earth. NASA Astrobiology/Mike Toillion For an example of geological evidence of microbial metabolism, we can consider the formation of banded iron formations (BIFs) on the ancient seafloor. These colorful layers of alternating iron- and silicon-rich sediment were formed from 3.8 billion to 1.8 billion years ago and are associated with some of the oldest rock formations on Earth. The red colors they exhibit are from their high iron content, showing us that the ocean of Earth was rich in iron during the 2 billion years in which these rocks were forming.
      Another way to study ancient microbial life is to look back along the evolutionary information contained in the genetics of life today. Combining this genetic information from molecular biology with geobiological information from the rock record can help astrobiologists understand the connections between the shared evolution of the early Earth and early life.
      In the new study, the team of researchers provide a review of current knowledge, gleaning information into the early metabolisms used by microbial life, the timing of when these metabolisms evolved, and how these processes are linked to major chemical and physical changes on Earth, such as the oxygenation of the oceans and atmosphere.
      Over time, the prevalence of oxygen on Earth has varied dramatically, in the ocean, in the atmosphere, and on land. These changes impacted both the evolution of the biosphere and the environment. For instance, as the activity of photosynthetic organisms raised oxygen levels in the atmosphere, creating new environments for microbial life to inhabit. Different nutrients were made accessible to life to fuel growth. At the same time, microbes that couldn’t survive in the presence of oxygen had to adapt, perish, or find a way to survive in environments where oxygen didn’t persist, such as deep in the Earth’s subsurface.
      Rocks along the shoreline of Lake Salda in Turkey were formed over time by microbes that trap minerals in the water. These microbialites were once a major form of life on Earth. The new study explains our understanding of how oxygen levels have changed over time and spatial scales. The authors map different types of microbial metabolism, such as photosynthesis, to this history to better understand the “cause-and-effect relationship” between oxygen and the evolution of life on Earth. The paper provides important context for major changes in the course of evolution for the biosphere and the planet.
      By carefully considering the history of different types of microbial metabolisms on Earth, the review paper shows how biogeochemical cycles on our planet are inextricably linked through time over both local and global scales. The authors also discuss significant gaps in our knowledge that limit interpretations. For instance, we do not know how large the young biosphere on Earth was, which limits our ability to estimate the global effects of various metabolisms during Earth’s earliest years. Similarly, when using genetic information to look back along the tree of life, scientists can estimate when certain genes first appeared (and thereby what types of metabolisms could have been used at the time in living cells). However, the evolution of a new type of metabolism at a point in history does not necessarily mean that that metabolism was common or had a large enough effect in the environment to leave evidence in the rock record.
      According to the authors, “The history of microbial life marched in step with the history of the
      oceans, land and atmosphere, and our understanding remains limited by how much we still do not know about the environments of the early Earth.”
      This is an illustration of exoplanet WASP-39 b, also known as Bocaprins. NASA’s James Webb Space Telescope provided the most detailed analysis of an exoplanet atmosphere ever with WASP-39 b analysis released in November 2022. Webb’s Near-Infrared Spectrograph (NIRSpec) showed unambiguous evidence for carbon dioxide in the atmosphere, while previous observations from NASA’s Hubble and Spitzer Space Telescopes, as well as other telescopes, indicate the presence of water vapor, sodium, and potassium. The planet probably has clouds and some form of weather, but it may not have atmospheric bands like those of Jupiter and Saturn. This illustration is based on indirect transit observations from Webb as well as other space and ground-based telescopes. Webb has not captured a direct image of this planet. NASA, ESA, CSA, Joseph Olmsted (STScI) The study also has wider implications in the search for life beyond Earth. Understanding the co-evolution of life and the environment can help scientists better understand the conditions necessary for a planet to be habitable. The interconnections between life and the environment also provide important clues in the search for biosignature gases in the atmospheres of planets that orbit distant stars.
      The study, “Co‐evolution of early Earth environments and microbial life,” was published in the journal Nature Reviews. Additional information on the study is available from the University of California, Riverside.
      Click here to return to the NASA Astrobiology page.
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    • By NASA
      2 min read
      Voyager 1 Returning Science Data From All Four Instruments
      An artist’s concept of the Voyager spacecraft. NASA/JPL-Caltech The spacecraft has resumed gathering information about interstellar space.
      NASA’s Voyager 1 spacecraft is conducting normal science operations for the first time following a technical issue that arose in November 2023.
      The team partially resolved the issue in April when they prompted the spacecraft to begin returning engineering data, which includes information about the health and status of the spacecraft. On May 19, the mission team executed the second step of that repair process and beamed a command to the spacecraft to begin returning science data. Two of the four science instruments returned to their normal operating modes immediately. Two other instruments required some additional work, but now, all four are returning usable science data.  
      The four instruments study plasma waves, magnetic fields, and particles. Voyager 1 and Voyager 2 are the only spacecraft to directly sample interstellar space, which is the region outside the heliosphere — the protective bubble of magnetic fields and solar wind created by the Sun.
      While Voyager 1 is back to conducting science, additional minor work is needed to clean up the effects of the issue. Among other tasks, engineers will resynchronize timekeeping software in the spacecraft’s three onboard computers so they can execute commands at the right time. The team will also perform maintenance on the digital tape recorder, which records some data for the plasma wave instrument that is sent to Earth twice per year. (Most of the Voyagers’ science data is sent directly to Earth and not recorded.)
      Voyager 1 is more than 15 billion miles (24 billion kilometers) from Earth, and Voyager 2 is more than 12 billion miles (20 billion kilometers) from the planet. The probes will mark 47 years of operations later this year. They are NASA’s longest-running and most-distant spacecraft. Both spacecraft flew past Jupiter and Saturn, while Voyager 2 also flew past Uranus and Neptune.
      News Media Contact
      Calla Cofield
      Jet Propulsion Laboratory, Pasadena, Calif.
      626-808-2469
      calla.e.cofield@jpl.nasa.gov
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