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By NASA
Scientists find that cometary dust affects interpretation of spacecraft measurements, reopening the case for comets like 67P as potential sources of water for early Earth.
Researchers have found that water on Comet 67P/Churyumov–Gerasimenko has a similar molecular signature to the water in Earth’s oceans. Contradicting some recent results, this finding reopens the case that Jupiter-family comets like 67P could have helped deliver water to Earth.
Water was essential for life to form and flourish on Earth and it remains central for Earth life today. While some water likely existed in the gas and dust from which our planet materialized around 4.6 billion years ago, much of the water would have vaporized because Earth formed close to the Sun’s intense heat. How Earth ultimately became rich in liquid water has remained a source of debate for scientists.
Research has shown that some of Earth’s water originated through vapor vented from volcanoes; that vapor condensed and rained down on the oceans. But scientists have found evidence that a substantial portion of our oceans came from the ice and minerals on asteroids, and possibly comets, that crashed into Earth. A wave of comet and asteroid collisions with the solar system’s inner planets 4 billion years ago would have made this possible.
This image, taken by ESA’s Rosetta navigation camera, was taken from a about 53 miles from the center of Comet 67P/Churyumov-Gerasimenko on March 14, 2015. The image resolution is 24 feet per pixel and is cropped and processed to bring out the details of the comet’s activity. ESA/Rosetta/NAVCAM While the case connecting asteroid water to Earth’s is strong, the role of comets has puzzled scientists. Several measurements of Jupiter-family comets — which contain primitive material from the early solar system and are thought to have formed beyond the orbit of Saturn — showed a strong link between their water and Earth’s. This link was based on a key molecular signature scientists use to trace the origin of water across the solar system.
This signature is the ratio of deuterium (D) to regular hydrogen (H) in the water of any object, and it gives scientists clues about where that object formed. Deuterium is a rare, heavier type — or isotope — of hydrogen. When compared to Earth’s water, this hydrogen ratio in comets and asteroids can reveal whether there’s a connection.
Because water with deuterium is more likely to form in cold environments, there’s a higher concentration of the isotope on objects that formed far from the Sun, such as comets, than in objects that formed closer to the Sun, like asteroids.
Measurements within the last couple of decades of deuterium in the water vapor of several other Jupiter-family comets showed similar levels to Earth’s water.
“It was really starting to look like these comets played a major role in delivering water to Earth,” said Kathleen Mandt, planetary scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. Mandt led the research, published in Science Advances on Nov. 13, that revises the abundance of deuterium in 67P.
About Kathleen Mandt
But in 2014, ESA’s (European Space Agency) Rosetta mission to 67P challenged the idea that Jupiter-family comets helped fill Earth’s water reservoir. Scientists who analyzed Rosetta’s water measurements found the highest concentration of deuterium of any comet, and about three times more deuterium than there is in Earth’s oceans, which have about 1 deuterium atom for every 6,420 hydrogen atoms.
“It was a big surprise and it made us rethink everything,” Mandt said.
Mandt’s team decided to use an advanced statistical-computation technique to automate the laborious process of isolating deuterium-rich water in more than 16,000 Rosetta measurements. Rosetta made these measurements in the “coma” of gas and dust surrounding 67P. Mandt’s team, which included Rosetta scientists, was the first to analyze all of the European mission’s water measurements spanning the entire mission.
The researchers wanted to understand what physical processes caused the variability in the hydrogen isotope ratios measured at comets. Lab studies and comet observations showed that cometary dust could affect the readings of the hydrogen ratio that scientists detect in comet vapor, which could change our understanding of where comet water comes from and how it compares to Earth’s water.
What are comets made of? It’s one of the questions ESA’s Rosetta mission to comet 67P/Churyumov-Gerasimenko wanted to answer. “So I was just curious if we could find evidence for that happening at 67P,” Mandt said. “And this is just one of those very rare cases where you propose a hypothesis and actually find it happening.”
Indeed, Mandt’s team found a clear connection between deuterium measurements in the coma of 67P and the amount of dust around the Rosetta spacecraft, showing that the measurements taken near the spacecraft in some parts of the coma may not be representative of the composition of a comet’s body.
As a comet moves in its orbit closer to the Sun, its surface warms up, causing gas to release from the surface, including dust with bits of water ice on it. Water with deuterium sticks to dust grains more readily than regular water does, research suggests. When the ice on these dust grains is released into the coma, this effect could make the comet appear to have more deuterium than it has.
Mandt and her team reported that by the time dust gets to the outer part of the coma, at least 75 miles from the comet body, it is dried out. With the deuterium-rich water gone, a spacecraft can accurately measure the amount of deuterium coming from the comet body.
This finding, the paper authors say, has big implications not only for understanding comets’ role in delivering Earth’s water, but also for understanding comet observations that provide insight into the formation of the early solar system.
“This means there is a great opportunity to revisit our past observations and prepare for future ones so we can better account for the dust effects,” Mandt said.
By Lonnie Shekhtman
NASA’s Goddard Space Flight Center, Greenbelt, Md.
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Last Updated Dec 03, 2024 Editor Lonnie Shekhtman Contact Lonnie Shekhtman lonnie.shekhtman@nasa.gov Location Goddard Space Flight Center Related Terms
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By NASA
A mentor of research scientist Meloë Kacenelenbogen once shared a sentiment from French author André Gide: “You cannot discover new oceans unless you have the courage to lose sight of the shore.” Kacenelenbogen pushes beyond her comfort zone to explore the unknown.
Name: Meloë S. Kacenelenbogen
Formal Job Classification: Research scientist
Organization: Climate and Radiation Laboratory, Science Directorate (Code 613)
Dr. Meloë S. Kacenelenbogen is a research scientist at NASA’s Goddard Space Flight Center in Greenbelt, Md. She studies the impact of aerosols on air quality and the Earth’s climate.Photo courtesy of Meloë Kacenelenbogen What do you do and what is most interesting about your role here at Goddard?
I study the impact of aerosols — suspended particles from, for example, wildfire smoke, desert dust, urban pollution, and volcanic eruptions — on air quality and the Earth’s climate. I use space, air, and ground-based observations, as well as models.
Why did you become a scientist? What is your educational background?
I never made a deliberate choice to become a scientist. I started with very little confidence as a child and then built up my confidence by achieving things I thought I could not do. I chose the hardest fields to work on along the way. Science looked hard and so did fluid mechanics, remote sensing, and atmospheric physics. I have failed many times, but I always learn something and move on. I do get scared and maybe even paralyzed for a day or two, but I never let fear or failure immobilize me for long.
I was born in Maryland, but my family moved to France when I was young, so I am fluent in French. I have a bachelor’s and master’s degree in mechanical engineering, and physical methods in remote sensing from the Université Pierre et Marie Curie (Paris VI, Jussieu). In 2008, I got a Ph.D. in atmospheric physics for applying satellite remote sensing to air quality at the Université des Sciences et Technologies de Lille (USTL), France.
What are some of your career highlights?
After my Ph.D., I worked for the Atmospheric Lidar Group at the University of Maryland, Baltimore County (UMBC), on spaceborne and ground-based lidars. In 2009, I got a NASA Post-doctoral Program (NPP) fellowship at the agency’s Ames Research Center in California’s Silicon Valley, where I worked for 13 years on space-based, aircraft-based, and ground-based atmospheric aerosol vertical distribution and aerosol typing.
In 2022, I came to work at the Climate and Radiation Lab at Goddard.
What is most interesting about aerosols?
Aerosols are very topical because they have a huge impact on the air we breathe and our Earth’s climate. The smaller the aerosol, the deeper it can get into our lungs. Among other sources, aerosols can come from cars, factories, or wildfires. We all know that wildfires are becoming bigger and more frequent. They are expected to happen even more frequently in the future due to climate change. Both when I was living in California and here in Maryland, I have experienced first-hand choking from the wildfire smoke. I will always remember how apocalyptic it felt back in the summer of 2020 in California when wildfire smoke was paired with COVID confinement, and the sky turned Mars-like orange.
Please tell us about your involvement with the Atmosphere Observing System (AOS)?
I am incredibly lucky to be able to contribute to the next generation of NASA’s satellites. I am working on AOS, which will observe aerosols, clouds, convention, and precipitation in the Earth’s atmosphere. I am part of the team that is helping design several instruments and algorithms.
My role is to connect this spaceborne observing system to all our other space, ground, and air-based measurements at the time of launch. We are making a mesh of observations to address the science questions, run the algorithms, and validate the spaceborne measurements. I am constantly pushed to expand my horizon and my own knowledge.
Why do you enjoy always challenging yourself intellectually?
I started that way. I had no confidence, so I felt that the only way I could build my confidence was to try doing things that scared me. I may sometimes be a little scared, but I am never bored.
What did you learn from your mentors?
A few years ago, a mentor shared a quote from André Gide with me that encapsulates what we are talking about: “You cannot discover new oceans unless you have the courage to lose sight of the shore.” In other words, it is OK, maybe preferable, to be out of my comfort zone to explore the unknown as scary as it may be.
Along the way, it has been extremely important for me to deliberately choose mentors. To me, a good mentor has earned the respect of all who have worked with them, is uplifting, reassuring, and gives me the invaluable guidance and support that I need. I deliberately try to surround myself with the right people. I have been very, very fortunate to find incredible people to encourage me.
As a mentor, what do you advise?
I tell them to deliberately choose their mentors. I also tell them that it is OK to be uncomfortable. Being uncomfortable is the nature of our field. To do great things, we often need to be uncomfortable.
Why do you enjoy working on a team?
I love working on teams, I love to feed off the positive energy of a team whether I lead it or am part of it. In my field, teamwork with a positive energy is incredibly satisfying. Everybody feeds off everybody’s energy, we go further, are stronger, and achieve more. This may not happen often, but when it does it makes it all worth it.
What are the happiest moments in your career?
I am always happiest when the team publishes a paper and all our efforts, are encapsulated in that one well-wrapped and satisfying peer-reviewed paper that is then accessible to everyone online. Every paper we publish feels, to me, the same as a Ph.D. in terms of the work, pain, energy, and then, finally, satisfaction involved.
What do you hope to achieve in your career?
I want to have been a major contributor to the mission by the time the AOS satellites launch.
What do you do for fun?
I do mixed martial arts. I love the ocean, diving, and sailing. I also love going to art galleries, especially to see impressionist paintings to reconnect with my Parisian past.
Meloë Kacenelenbogen once shared a sentiment from French author André Gide: “You cannot discover new oceans unless you have the courage to lose sight of the shore.”Photo courtesy of Meloë Kacenelenbogen Who is your favorite author?
I love Zweig, Kafka, Dostoyevsky, Saint-Exupéry, and Kessel. The latter two wrote a lot about aviators in the early 1900s back in the days when it was new and very dangerous. Those pilots, like Mermoz, were my heroes growing up.
Who would you like to thank?
I would like to thank my family for being my rock.
What are your guiding principles?
To paraphrase Dostoevsky, everyone is responsible to all men for all men and for everything. I have a strong sense of purpose, pride, justice, and honor. This is how I try to live my life for better or for worse.
By Elizabeth M. Jarrell
NASA’s Goddard Space Flight Center, Greenbelt, Md.
Conversations With Goddard is a collection of Q&A profiles highlighting the breadth and depth of NASA’s Goddard Space Flight Center’s talented and diverse workforce. The Conversations have been published twice a month on average since May 2011. Read past editions on Goddard’s “Our People” webpage.
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Last Updated Oct 22, 2024 EditorMadison OlsonContactRob Garnerrob.garner@nasa.govLocationGoddard Space Flight Center Related Terms
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By NASA
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Preparations for Next Moonwalk Simulations Underway (and Underwater)
The Oceans group, from the 2024 Student Airborne Research Program (SARP) West Coast cohort, poses in front of the natural sciences building at UC Irvine, during their final presentations on August 13, 2024. NASA Ames/Milan Loiacono Faculty Advisor: Dr. Henry Houskeeper, Woods Hole Oceanographic Institute
Graduate Mentor: Lori Berberian, University of California, Los Angeles
Lori Berberian, Graduate Mentor
Lori Berberian graduate student mentor for the 2024 SARP West Oceans group, provides an introduction for each of the group members and shares behind-the scenes moments from the internship.
Emory Gaddis
Leveraging High Resolution PlanetScope Imagery to Quantify oil slick Spatiotemporal Variability in the Santa Barbara Channel
Emory Gaddis, Colgate University
Located within the Santa Barbara Channel of California, Coal Oil Point is one of the world’s largest hydrocarbon seep fields. The area’s natural hydrocarbon seepage and oil production have sustained both scientific interest and commercial activity for decades. Historically, indigenous peoples in the region utilized the naturally occurring tar for waterproofing baskets, establishing early evidence of the natural presence of hydrocarbons long before modern oil extraction began. Gaseous hydrocarbons are released from the marine floor through the process of seeping, wherein a buildup of reservoir pressure relative to hydrostatic pressure causes bubbles, oily bubbles, and droplets to rise to the surface. This hydrocarbon seepage is a significant source of Methane CH4—a major greenhouse gas––emissions into the atmosphere. Current limitations of optical remote sensing of oil presence and absence in the ocean leverage geometrical as well as biogeochemical factors and include changes in observed sun glint, sea surface damping, and wind roughening due to changes in surface oil concentrations. We leverage high-resolution (3m) surface reflectance observations obtained from PlanetScope to construct a time series of oil slick surface area spanning 2017 to 2023 within the Coal Oil Point seep field. Our initial methods are based on manual annotations performed within ArcGIS-Pro. We assess potential relationships between wind speed and oil slick surface area to support a sensitivity analysis of our time series. Correcting for confounding outside factors (e.g., wind speed) that modify oil slick surface area improves determination of oil slick surface area and helps test for changes in natural seepage rates and whether anthropogenic activities, such as oil drilling, alter natural oil seepage. Future investigations into oil slick chemical properties and assessing how natural seepage impacts marine and atmospheric environments (e.g., surface oil releases methane into the atmosphere) can help to inform the science of optimizing oil extraction locations.
Rachel Emery
Investigating Airborne LiDAR Retrievals of an Emergent South African Macroalgae
Rachel Emery, The University of Oklahoma
Right now, the world is facing an unprecedented biodiversity crisis, with areas of high biodiversity at the greatest risk of species extinction. One of these biodiversity hotspots, the Western Cape Province of South Africa, features one of the world’s largest unique marine ecosystems due to the extensive growth of canopy forming kelps, such as Macrocystis and Ecklonia, which provide three-dimensional structure important for fostering biodiversity and productivity. Canopy-forming kelps face increasing threats by marine heatwaves and pollution related to climate change and local water quality perturbation. Though these ecosystems can be monitored using traditional field surveying methods, remote sensing via airborne and satellite observations support improved spatial coverage and resample rates, plus extensive historical continuity for tracking multidecadal scale changes. Passive remote sensing observations—such as those derived using observations from NASA’s Airborne Visible-Infrared Imaging Spectrometer – Next Generation (AVIRIS-NG) —provide high resolution, hyperspectral imagery of oceanic environments anticipated to help characterize community dynamics and quantify macroalga physiological change. Active remote sensing observations, e.g., Light Detection and Ranging (LiDAR), are less understood in terms of applications to marine ecosystems, but are anticipated to support novel observations of vertical structure not supported using passive aquatic remote sensing. Here we investigate the potential to observe an emergent canopy-forming macroalgae (i.e., Ecklonia, which can extend more than a decimeter above the ocean’s surface) using NASA’s Land, Vegetation, and Ice sensor (LVIS), which confers decimeter-scale vertical resolution. We validate LVIS observations using matchup observations from AVIRIS-NG imagery to test whether LiDAR remote sensing can improve monitoring of emergent kelps in key biodiversity regions such as the Western Cape.
Brayden Lipscomb
Vertical structure of the aquatic light field based on half a century of oceanographic records from the southern California Current
Brayden Lipscomb, West Virginia University
Understanding the optical properties of marine ecosystems is crucial for improving models related to oceanic productivity. Models relating satellite observations to oceanic productivity or subsurface (e.g., benthic) light availability often suffer from uncertainties in parameterizing vertical structure and deriving columnar parameters from surface observations. The most accurate models use in situ station data, minimizing assumptions such as atmospheric optical thickness or water column structure. For example, improved accuracy of satellite primary productivity models has previously been demonstrated by incorporating information on vertical structure obtained from gliders and floats. We analyze vertical profiles in photosynthetically available radiation (PAR) obtained during routine surveys of the southern California Current system by the California Cooperative Oceanic Fisheries Investigation (CalCOFI). We find that depths of 1% and 10% light availability show coherent log-linear relationships with attenuation measured near surface (i.e., within the first 10 m), despite vertical variability in water column constituent concentrations and instrumentation challenges related to sensitivity, self-shading, and ship adjacency. Our results suggest that subsurface optical properties can be more reliably parameterized from near-surface measurements than previously understood.
Dominic Bentley
Comparing SWOT and PACE Satellite Observations to Assess Modification of Phytoplankton Biomass and Assemblage by North Atlantic Ocean Eddies
Dominic Bentley, Pennsylvania State University
Upwelling is the shoaling of the nutricline, thermocline, and isopycnals due to advection by eddies of the surface ocean layer. This shoaling effect leads to an increase in the productivity of algal blooms in a given body of water. Mesoscale to deformation scale eddy circulation modulates productivity based on latitude, season, direction, and other physical factors. However, many processes governing the effects of eddies on the ocean microbial environment remain unknown due to limitations in observations linking eddy strength and direction with productivity and ocean biogeochemistry. Currently, satellites are the only ocean observing system that allows for broad spatial coverage with high resample rates, albeit with limitations due to cloud obstructions (including storms that may stimulate productivity) and to observations being limited to the near-surface. A persisting knowledge gap in oceanography stems from limitations in the spatial resolution of observations resolving submesoscale dynamics. The recent launch of the Surface Water and Ocean Topography (SWOT) mission in December of 2022 supports observations of upper-ocean circulation with increased resolution relative to legacy missions (e.g. TOPEX/Poseidon, Jason-1, OSTM/Jason-2). Meanwhile, the launch of the Plankton, Aerosol, Cloud, ocean Ecosystem (PACE) satellite in February of 2024 is anticipated to improve knowledge of ocean microbial ecosystem dynamics. We match up SWOT observations of sea surface height (SSH) anomalies—informative parameters of eddy vorticity—with PACE observations of surface phytoplankton biomass and community composition to relate the distribution of phytoplankton biomass and assemblage structure to oceanic eddies in the North Atlantic. We observe higher concentrations of Chlorophyll a (Chla) within SSH minima indicating the stimulation of phytoplankton productivity by cyclonic features associated with upwelling-driven nutrient inputs.
Abigail Heiser
Assessing EMIT observations of harmful algae in the Salton Sea
Abigail Heiser, University of Wisconsin- Madison
In 1905, flooding from the Colorado River gave rise to what would become California’s largest lake, the Salton Sea. Today, the majority of its inflow is sourced from agricultural runoff, which is rich in fertilizers and pollutants, leading to elevated lake nutrient levels that fuel harmful algal blooms (HAB) events. Increasingly frequent HAB events pose ecological, environmental, economic, and health risks to the region by degrading water quality and introducing environmental toxins. Using NASA’s Earth Surface Mineral Dust Source Investigation (EMIT) imaging spectrometer we apply two hyperspectral aquatic remote sensing algorithms; cyanobacteria index (CI) and scattering line height (SLH). These algorithms detect and characterize spatiotemporal variability of cyanobacteria, a key HAB taxa. Originally designed to study atmospheric mineral dust, EMIT’s data products provide novel opportunities for detailed aquatic characterizations with both high spatial and high spectral resolution. Adding aquatic capabilities for EMIT would introduce a novel and cost-effective tool for monitoring and studying the drivers and timing of HAB onset, to improve our understanding of environmental dynamics.
Emma Iacono
Reassessing multidecadal trends in Water Clarity for the central and southern California Current System
Emma Iacono, North Carolina State University
Over the past several decades, the world has witnessed a steady rise in average global temperatures, a clear indication of the escalating effects of climate change. In 1990, Andrew Bakun hypothesized that unequal warming of sea and land surface temperatures would increase pressure gradients and lead to rising rates of alongshore upwelling within Eastern Boundary Currents, including the California Current System (CCS). An anticipated increase in upwelling-favorable winds would have profound implications for the productivity of the CCS, wherein upwelled waters supply nutrient injections that sustain and fuel coastal ocean phytoplankton stocks. Increasing upwelling, therefore, is anticipated to increase the turbidity of the upper ocean, corresponding with greater phytoplankton concentrations. Historical observations of turbidity are supported by observations obtained using a Secchi Disk, i.e., an opaque white instrument lowered into the water column. Observations of Secchi depth—or the depth at which light reflected from the Secchi Disk is no longer visible from the surface—provide a quantification of light penetration into the euphotic zone. The shoaling, or shallowing, of Secchi disk depths was previously reported for inshore, transition, and offshore waters of the central and southern CCS for historical observations spanning 1969 – 2007. Here, we reassess Secchi disk depths during the subsequent period spanning 2007 to 2021 and test for more recent changes in water clarity. Additionally, we evaluate the seasonality and spatial patterns of Secchi disk trends to test for potential changes to oceanic microbial ecology. Indications of long-term trends in some of the coastal domains assessed were found. Generally, our findings suggest a reversal of the trends previously reported. In particular, increases in water clarity likely associated with a recent marine heatwave (MHW) may be responsible for recent changes in Secchi disk depth observations, illustrating the importance of MHW events for modifying the CCS microbial ecosystem.
Click here watch the Atmospheric Aerosols Group presentations.
Click here watch the Terrestrial Ecology Group presentations.
Click here watch the Whole Air Sampling (WAS) Group presentations.
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Last Updated Sep 25, 2024 Related Terms
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