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Aura at 20 Years
Introduction
In the 1990s and early 2000s, an international team of engineers and scientists designed an integrated observatory for atmospheric composition – a bold endeavor to provide unprecedented detail that was essential to understanding how Earth’s ozone (O3) layer and air quality respond to changes in atmospheric composition caused by human activities and natural phenomena. This work addressed a key NASA Earth science objective. Originally referred to as Earth Observing System (EOS)–CHEM (later renamed Aura,) the mission would become the third EOS Flagship mission, joining EOS-AM 1 (Terra) launched in 1999 and EOS-PM 1 (Aqua), launched in 2002. The Aura spacecraft – see Figure 1 – is similar in design to Terra and identical to Aqua. Aura and its four instruments were launched on July 15, 2004 from Vandenberg Air Force Base (now Space Force Base) in California – see Photo.
Figure 1. An artist’s representation of the Aura satellite in orbit around the Earth. Image credit: NASA Photo. A photo of the nighttime launch of Aura on July 15, 2004. Image credit: NASA In 2014 The Earth Observer published an article called “Aura Celebrates Ten Years in Orbit,” [Nov–Dec 2014, 26:6, pp. 4–18] which details the history of Aura and the first decade of science resulting from its data. Therefore, the current article will focus on the science and applications enabled by Aura data in the last decade. It also examines Aura’s future and the legacies of the spacecraft’s instruments. Readers interested in more information on Aura and the scientific research and applications enabled by its data can visit the Aura website.
Recent Science Achievements from Aura’s Instrument (in alphabetical order)
High Resolution Dynamics Limb Sounder
The capabilities of the High Resolution Dynamics Limb Sounder (HIRDLS) were compromised at launch and operations ceased in March 2008 due to an image chopper stall. Nevertheless, the HIRDLS team was able to produce a three-year dataset notable for high vertical resolution profiles of greater than 1 km (0.62 mi) for temperature and O3 in the upper troposphere to the mesosphere. Though limited, the HIRDLS dataset demonstrated the incredible potential of the instrument for atmospheric research. So much so, that scientists are now in the study phase for a new instrument, part of the proposed Stratosphere Troposphere Response using Infrared Vertically-Resolved Light Explorer (STRIVE) mission, which would have similar capabilities as HIRDLS with advancements in spectral and spatial imaging. (STRIVE is one of four missions currently undergoing one-year concept studies, as part of NASA’s Earth System Explorer Program, which was established in the 2017 Earth Science Decadal Survey. Two winning proposals will be chosen in 2025 for full development and launch in 2030 or 2032.)
Microwave Limb Sounder
The Microwave Limb Sounder (MLS) was developed to study: 1) the evolution and recovery of the stratospheric O3 layer; 2) the role of the stratosphere, notably stratospheric humidity, in climate feedback processes; and 3) the behavior of air pollutants in the upper troposphere. MLS measures vertical profiles from the upper troposphere at ~10 km altitude (6.2 mi) to the mesosphere at ~90 km (56 mi) of 16 trace gases, temperature, geopotential height, and cloud ice. Its unique measurement suite has made it the “go-to” instrument for most data-driven studies of middle atmosphere composition over the last two decades.
Data collection during the past decade has highlighted the ability of the stratosphere to exhibit surprising and/or envelope-redefining behavior, (Envelope-redefining is a term that is used to refer to an event that greatly exceeded previous observed ranges of this event.) MLS observations have been crucial for the discovery and diagnoses of these extreme events. For example, in 2019, a stratospheric sudden warming over the southern polar cap in September – rare in the Antarctic – curtailed chemical processing, leading to an anomalously weak O3 hole. As another example, prolonged hot and dry conditions in Australia during the subsequent 2019–2020 southern summer promoted the catastrophic “Australian New Year” (ANY) fires. MLS observations showed that fire-driven pyrocumulonimbus convection lofted plumes of polluted air into the stratosphere to a degree never seen during the Aura mission.
Apart from those individual plumes, smoke pervaded the southern lower stratosphere, leading to unprecedented perturbations in southern midlatitude lower stratospheric composition, with chlorine (Cl) shifting from its main reservoir species, hydrochloric acid (HCl), into the O3-destroying form, hypochlorite (ClO). Peak anomalies in chlorine species occurred in mid-2020 – months after the fires. State-of-the-art atmospheric chemistry models in which wildfire smoke has properties similar to those of sulfate (SO4) aerosols were unable to reproduce the observed chemical redistribution. New model simulations assuming that HCl dissolves more readily in smoke than in SO4 particles under typical midlatitude stratospheric conditions better match the MLS observations.
As extraordinary as these events were, their impacts on the stratosphere were spectacularly eclipsed by the impact of the January 2022 eruption of the Hunga Tonga-Hunga Ha’apai (Hunga) volcano in the Pacific Ocean. The Hunga eruption lofted about 150 Tg of water vapor into the stratosphere – with initial injections reaching into the mesosphere. The eruption almost instantaneously increased total stratospheric water vapor by about 10%. MLS was the only sensor able to track the plume in the first weeks following the eruption. The Hunga humidity enhancement resulted in an envelope-redefining, low-temperature anomaly in the stratosphere, in turn inducing changes in stratospheric circulation. Repartitioning of southern midlatitude Cl also occurred, though to a lesser degree than following the ANY fires and in a manner broadly consistent with known chemical mechanisms. The Hunga water vapor enhancement has not substantially declined in the 2.5 years since the eruption, and studies indicate that it will likely endure for several more years.
Impacts of the Hunga humidity on polar O3 loss have also been investigated. The timing and location of the eruption were such that the plume reached high southern latitudes only after the 2022 Antarctic winter vortex had developed. Since the strong winds at the vortex edge present a transport barrier, polar stratospheric cloud (PSC) formation and O3 hole evolution were largely unaffected. When the vortex broke down at the end of the 2022 Antarctic winter, moist air flooded the southern polar region, increasing humidity in the region. Cold, moist conditions led to unusually early and vertically extensive PSC formation and Cl activation, but chemical processing ran to completion by mid-July, as typically occurs in southern winter. The cumulative chemical O3 losses ended up being unremarkable throughout the lower stratosphere. The Hunga plume was also largely excluded from the 2022–2023 Arctic vortex. The 2023–2024 Arctic O3 loss season was characterized by conditions that were dynamically disturbed and not persistently cold, and springtime O3 was near or above average. The extraordinary stratospheric hydration from Hunga has so far had minimal impact on chemical processing and O3 loss in the polar vortices in either hemisphere – see Figure 2.
Figure 2. The evolution of MLS water vapor anomalies (deviations from the baseline 2005–2021 climatology) from January 2019 through December 2023 as a function of equivalent latitude at 700 K potential temperature in the middle stratosphere at ~27 km altitude (17 mi). Black contours mark the approximate edge of the polar vortex. The green triangle marks the time of the main Hunga eruption at latitude 20.54°S on January 15, 2022. Figure credit: Updated and adapted from a 2023 paper in Geophysical Research Letters With the end of Aura and MLS, the future for stratospheric limb sounding observations is unclear. While stratospheric O3 and aerosol will continue to be measured on a daily, near-global basis by the Ozone Mapping and Profiler Suite (OMPS) Limb Profiler (OMPS-LP) instruments on the Suomi National Polar-orbiting Partnership (Suomi NPP) and Joint Polar Satellite System (JPSS-2, -3, and -4) satellites, there are no confirmed plans for daily, near-global observations of either long-lived trace gases or halogenated species – both of which are needed to diagnose observed changes in O3. The only other sensor making such measurements, the Canadian Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE–FTS), is itself older than MLS and, as a solar occultation instrument, measures only 30 profiles-per-day, taking around a month to cover all latitudes. Similarly, no other sensor is set to provide daily, near-global measurements of stratospheric water vapor until the launch of the Canadian High-altitude Aerosols, Water vapour and Clouds (HAWC) mission in the early 2030s. Some potential new mission concepts are under consideration by both NASA and ESA, but they are subject to competition. Even if both instruments are ultimately selected, gaps in the records of many species measured by MLS are inevitable. The MLS PI is leading an effort to develop new technologies that would allow an instrument that could restart MLS measurements to be built in a far smaller mass/power footprint (e.g., 60 kg, 90 W vs. 500 kg, 500 W for Aura MLS), and technologies exist for yet-smaller MLS-like instruments that could assume the legacy of the highly impactful MLS record at low cost in future decades.
Ozone Monitoring Instrument
The Ozone Monitoring Instrument (OMI) continues the Total Ozone Mapping Spectrometer (TOMS) record for total O3 and other atmospheric parameters related to O3 chemistry and climate. It employs hyperspectral imaging in a push-broom mode to observe solar backscatter radiation in the visible and ultraviolet.
OMI is a Dutch–Finnish contribution to the Aura mission, and its remarkable stability and revolutionary two-dimensional (2D) detector (spatial in one dimension and spectral in the other) has produced a two-decade record of science- and trend-quality datasets of atmospheric column observations. OMI continues the long-term record of total column O3 measurements begun in 1979, and its observations of nitrogen dioxide (NO2), sulfur dioxide (SO2), formaldehyde (CH2O), and absorbing aerosols provided exceptional spatial resolution for study of anthropogenic and natural trends and variations of these pollutants around the world. Its radiometric and spectral stability has made it a valuable contributor for solar spectral irradiance measurements to complement dedicated solar instruments on other satellites. The many achievements made possible with OMI are documented in a review article.
OMI’s multidecade data records have revolutionized the ability to monitor air quality changes around the world, even at the sub-urban level. In particular, OMI NO2 data have been transformative. Recently, these data were used to track changes in air pollution associated with efforts to control the spread of SARS-CoV-2. OMI’s long, stable data record allowed for changes in pollution levels in 2020 – at the height of global lockdowns – to be put into historical perspective, especially within the envelope of typical year-to-year variations associated with meteorological variability. Many research studies assessed the impact of the pandemic lockdowns on air pollution, supporting novel uses of OMI data for socioeconomic-related research. For example, OMI NO2 data were shown to serve as an environmental indicator to evaluate the effectiveness of lockdown measures and as a significant predictor for the deceleration of COVID-19 spread. OMI NO2 data were also used as a proxy for the economic impact of the pandemic as NO2 is emitted during fossil fuel combustion, which is another proxy for economic activity since most global economies are driven by fossil fuels – see Animation.
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Animation. OMI data show changes in average levels of NO2 from March 20 to May 20 for each year from 2015 to 2023 over the northeast U.S. Levels in 2020 were ~30% lower relative to previous years because of efforts to slow the spread of COVID-19. OMI data indicate similar reductions in NO2 in cities across the globe in early 2020 and a gradual recovery in pollutant emissions in late 2020 into 2023. Additional images for other world cities and regions are available through the NASA Science Visualization Studio website and the Air Quality Observations from Space website. Animation credit: NASA Science Visualization Studio OMI’s datasets are being continued by successor 2D detector array instruments, such as the previously mentioned Copernicus Sentinel-5P TROPOMI mission, the Republic of Korea’s Geostationary Environment Monitoring Spectrometer (GEMS), and NASA’s Tropospheric Emissions: Monitoring of Pollution (TEMPO). All of these missions have enhanced spatial resolution relative to OMI, but have benefited from the innovative retrieval algorithms pioneered by OMI’s retrieval teams.
Tropospheric Emission Spectrometer
The Tropospheric Emission Spectrometer (TES) provided vertically-resolved distributions of a number of tropospheric constituents, e.g., O3, methane (CH4), and various volatile organic compounds. The instrument was decommissioned in 2018 due to signs of aging associated with a failing Interferometer Control System motor encoder bearing. Nevertheless, TES measurements led to a number of key results regarding changes in atmospheric composition that were published over the past 10 years.
Measurements from TES, OMI, and MLS showed that transport of O3 and its precursors from East Asia offset about 43% of the decline expected in O3 over the western U.S., based on emission reductions observed there over the period 2005–2010. TES megacity measurements revealed that the frequency of high-O3 days is particularly pronounced in South Asian megacities, which typically lack ground-based pollution monitoring networks. TES water vapor and semi-heavy water measurements indicated that water transpired from Amazonian vegetation becomes a significant moisture source for the atmosphere, during the transition from dry to wet season. The increasing water vapor provides the fuel needed to start the next rainy season. Measurements of CH4 from TES and carbon monoxide (CO) from Measurements of Pollution in the Troposphere (MOPITT) on Terra showed that CH4 emissions from fires declined at twice the rate expected from changes in burned area from 2004–2014. This finding helped to balance the CH4 budget for this period, because it offset some of the large increases in fossil fuel and wetland emissions. Through direct measurement of the O3 greenhouse gas effect, TES instantaneous radiative kernels revealed the impact of hydrological controls on the O3 radiative forcing and were used to show substantial radiative bias in Intergovernmental Panel on Climate Change (IPCC) chemistry–climate models. The TES team pioneered the retrieval of a number of species, such as peroxyacetyl nitrate, carbonyl sulfide, and ethylene.
The spirit of TES lives on through the NASA TRopospheric Ozone and its Precursors from Earth System Sounding (TROPESS) project, which generates data products of O3 and other atmospheric constituents by processing data from multiple satellites through a common retrieval algorithm and ground data system. TROPESS builds upon the success of TES and is considered a bridge to allow the development of a continuous record of O3 and other trace gas species as a follow-on to TES.
Future of Aura
In April 2023, Aura’s mission operations team performed the last series of maneuvers to maintain its position in the A-Train constellation of satellites. Since then, Aura has begun drifting. As of July 2024, Aura has descended ~5 km (3 mi) in altitude from ~700 km (435 mi) and its equator crossing time has increased by ~9 min from ~1:44 PM local time. This amount of drift is small, and the Aura MLS and OMI retrieval teams are ensuring the science- and trend-quality of the datasets.
As Aura continues to drift, the amount of sunlight reaching its solar panels will slowly decrease and will no longer be able to generate sufficient power to operate the spacecraft and instruments by mid-2026. At this point, the amount of local time drift will still be relatively small – less than one hour – so the retrieval teams will be able to ensure quality for most data products until this time.
In the remaining years, Aura’s aging but remarkably stable instruments will continue to add to the unprecedented two decades of science- and trend-quality data of numerous key tropospheric and stratospheric constituents. Aura data will be key for monitoring the evolution of the Hunga volcanic plume and understanding its continued impact on the chemistry and dynamics of the stratosphere. Observations from MLS and OMI will also be used to evaluate data from new and upcoming instruments (e.g., ESA’s Atmospheric Limb Tracker for Investigation of Upcoming Stratosphere (Altius); NASA’s TEMPO, Plankton, Aerosol, Cloud, ocean Ecosystem (PACE), and Total and Spectral Solar Irradiance Sensor-2 (TSIS-2) missions, or at least used to help minimize the gaps between data collections.
Aura’s Scientific Legacy
The Aura mission has been nothing short of transformative for atmospheric research and applied sciences. The multidecade, stable datasets have furthered process-based understanding of the chemistry and dynamics of atmospheric trace gases, especially those critical for understanding the causes of trends and variations in Earth’s protective ozone layer.
The two decades that Aura has flown have been marked by profound atmospheric changes and numerous serendipitous events, both natural and man-made. The data from Aura’s instruments have given scientists and applied scientists an unparalleled view – including at the sub-urban scale – of air pollution around the world, clearly showing the influence of rapid industrialization, environmental regulations designed to improve air quality, seasonal agricultural burning, catastrophic wildfires, and even a global pandemic, on the air we breathe. The Aura observational record spans the period that includes the decline of O3-destroying substances, and Aura data illustrate the beginnings of the recovery of the Antarctic O3 hole, a result of unparalleled international cooperation to reduce these substances.
Aura’s datasets have given a generation of scientists the most comprehensive global view to date of critical gases in Earth’s atmosphere and the chemical and dynamic processes that shape their concentrations. Many, but not all, of these datasets are being/will be continued by successor instruments that have benefited from the novel technologies incorporated into the design of Aura’s instruments as well as the innovative retrieval algorithms pioneered by Aura’s retrieval teams.
Acknowledgements
The author wishes to acknowledge the decades of hard work of the many hundreds of people who have contributed to the success of the international Aura mission. There are too many to acknowledge here and I’m sure that many names from the early days are lost to time. I would like to offer special thanks to those scientists who, back in the 1980s, first dreamed of the mission that would become Aura.
Bryan Duncan
NASA’s Goddard Space Flight Center (GSFC)
bryan.n.duncan@nasa.gov
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Last Updated Sep 16, 2024 Related Terms
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By NASA
The Apollo 11 mission in July 1969 completed the goal set by President John F. Kennedy in 1961 to land a man on the Moon and return him safely to the Earth before the end of the decade. At the time, NASA planned nine more Apollo Moon landing missions of increasing complexity and an Earth orbiting experimental space station. No firm human space flight plans existed once these missions ended in the mid-1970s. After taking office in 1969, President Richard M. Nixon chartered a Space Task Group (STG) to formulate plans for the nation’s space program for the coming decades. The STG’s proposals proved overly ambitious and costly to the fiscally conservative President who chose to take no action on them.
Left: President John F. Kennedy addresses a Joint Session of Congress in May 1961. Middle: President Kennedy addresses a crowd at Rice University in Houston in September 1962. Right: President Lyndon B. Johnson addresses a crowd during a March 1968 visit to the Manned Spacecraft Center, now NASA’s Johnson Space Center, in Houston.
On May 25, 1961, before a Joint Session of Congress, President John F. Kennedy committed the United States to the goal, before the decade was out, of landing a man on the Moon and returning him safely to the Earth. President Kennedy reaffirmed the commitment during an address at Rice University in Houston in September 1962. Vice President Lyndon B. Johnson, who played a leading role in establishing NASA in 1958, under Kennedy served as the Chair of the National Aeronautics and Space Council. Johnson worked with his colleagues in Congress to ensure adequate funding for the next several years to provide NASA with the needed resources to meet that goal.
Following Kennedy’s assassination in November 1963, now President Johnson continued his strong support to ensure that his predecessor’s goal of a Moon landing could be achieved by the stipulated deadline. But with increasing competition for scarce federal resources from the conflict in southeast Asia and from domestic programs, Johnson showed less interest in any space endeavors to follow the Apollo Moon landings. NASA’s annual budget peaked in 1966 and began a steady decline three years before the agency met Kennedy’s goal. From a budgetary standpoint, the prospects of a vibrant, post-Apollo space program didn’t look all that rosy, the triumphs of the Apollo missions of 1968 and 1969 notwithstanding.
Left: On March 5, 1969, President Richard M. Nixon, left, introduces Thomas O. Paine as the NASA Administrator nominee, as Vice President Spiro T. Agnew looks on. Middle: Proposed lunar landing sites through Apollo 20, per August 1969 NASA planning. Right: An illustration of the Apollo Applications Program experimental space station that later evolved into Skylab.
Less than a month after assuming the Presidency in January 1969, Richard M. Nixon appointed a Space Task Group (STG), led by Vice President Spiro T. Agnew as the Chair of the National Aeronautics and Space Council, to report back to him on options for the American space program in the post-Apollo years. Members of the STG included NASA Acting Administrator Thomas O. Paine (confirmed by the Senate as administrator on March 20), the Secretary of Defense, and the Director of the Office of Science and Technology. At the time, the only approved human space flight programs included lunar landing missions through Apollo 20 and three long-duration missions to an experimental space station based on Apollo technology that evolved into Skylab.
Beyond a general vague consensus that the United States human space flight program should continue, no approved projects existed once these missions ended by about 1975. With NASA’s intense focus on achieving the Moon landing within President Kennedy’s time frame, long-term planning for what might follow the Apollo Program garnered little attention. During a Jan. 27, 1969, meeting at NASA chaired by Acting Administrator Paine, a general consensus emerged that the next step after the Moon landing should involve the development of a 12-person earth-orbiting space station by 1975, followed by an even larger outpost capable of housing up to 100 people “with a multiplicity of capabilities.” In June, with the goal of the Moon landing almost at hand, NASA’s internal planning added the development of a space shuttle by 1977 to support the space station, the development of a lunar base by 1976, and the highly ambitious idea that the U.S. should prepare for a human mission to Mars as early as the 1980s. NASA presented these proposals to the STG for consideration in early July in a report titled “America’s Next Decades in Space.”
Left: President Richard M. Nixon, right, greets the Apollo 11 astronauts aboard the U.S.S. Hornet after their return from the Moon. Middle: The cover page of the Space Task Group (STG) Report to President Nixon. Right: Meeting in the White House to present the STG Report to President Nixon. Image credit: courtesy Richard Nixon Presidential Library and Museum.
Still bathing in the afterglow of the successful Moon landing, the STG presented its 29-page report “The Post-Apollo Space Program: Directions for the Future” to President Nixon on Sep. 15, 1969, during a meeting at the White House. In its Conclusions and Recommendations section, the report noted that the United States should pursue a balanced robotic and human space program but emphasized the importance of the latter, with a long-term goal of a human mission to Mars before the end of the 20th century. The report proposed that NASA develop new systems and technologies that emphasized commonality, reusability, and economy in its future programs. To accomplish these overall objectives, the report presented three options:
Option I – this option required more than a doubling of NASA’s budget by 1980 to enable a human Mars mission in the 1980s, establishment of a lunar orbiting space station, a 50-person Earth orbiting space station, and a lunar base. The option required a decision by 1971 on development of an Earth-to-orbit transportation system to support the space station. The option maintained a strong robotic scientific and exploration program.
Option II – this option maintained NASA’s budget at then current levels for a few years, then anticipated a gradual increase to support the parallel development of both an earth orbiting space station and an Earth-to-orbit transportation system, but deferred a Mars mission to about 1986. The option maintained a strong robotic scientific and exploration program, but smaller than in Option I.
Option III – essentially the same as Option II but deferred indefinitely the human Mars mission.
In separate letters, both Agnew and Paine recommended to President Nixon to choose Option II.
Left: Illustration of a possible space shuttle, circa 1969. Middle: Illustration of a possible 12-person space station, circa 1969. Right: An August 1969 proposed mission scenario for a human mission to Mars.
The White House released the report to the public at a press conference on Sep. 17 with Vice President Agnew and Administrator Paine in attendance. Although he publicly supported a strong human spaceflight program, enjoyed the positive press he received when photographed with Apollo astronauts, and initially sounded positive about the STG options, President Nixon ultimately chose not to act on the report’s recommendations. Nixon considered these plans too grandiose and far too expensive and relegated NASA to one America’s domestic programs without the special status it enjoyed during the 1960s. Even some of the already planned remaining Moon landing missions fell victim to the budgetary axe.
On Jan. 4, 1970, NASA had to cancel Apollo 20 since the Skylab program needed its Saturn V rocket to launch the orbital workshop. In 1968, then NASA Administrator James E. Webb had turned off the Saturn V assembly line and none remained beyond the original 15 built under contract. In September 1970, reductions in NASA’s budget forced the cancellation of two more Apollo missions, and in 1971 President Nixon considered cancelling two more. He reversed himself and they flew as Apollo 16 and Apollo 17 in 1972, the final Apollo Moon landing missions.
Left: NASA Administrator James C. Fletcher, left, and President Richard M. Nixon announce the approval to proceed with space shuttle development in 1972. Middle: First launch of the space shuttle in 1981. Right: In 1984, President Ronald W. Reagan directs NASA to build a space station.
More than two years after the STG submitted its report, in January 1972 President Nixon directed NASA Administrator James C. Fletcher to develop the Space Transportation System, the formal name for the space shuttle, the only element of the recommendations to survive the budgetary challenges. NASA anticipated the first orbital flight of the program in 1979, with the actual first flight occurring two years later. Twelve years elapsed after Nixon’s shuttle decision when President Ronald W. Reagan approved the development of a space station, the second major component of the STG recommendation. 14 years later, the first element of that program reached orbit. In those intervening years, NASA had redesigned the original American space station, leading to the development of a multinational orbiting laboratory called the International Space Station. Humans have inhabited the space station continuously for the past quarter century, conducting world class and cutting edge scientific and engineering research. Work on the space station helps enable future programs, returning humans to the Moon and later sending them on to Mars and other destinations.
The International Space Station as it appeared in 2021.
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Sols 4304-4006: 12 Years, 42 Drill Holes, and Now… 1 Million ChemCam Shots!
In celebration of ChemCam’s milestone, here is a stunning image from its remote micro imager, showing details in the landscape far away. This image was taken by Chemistry & Camera (ChemCam) onboard NASA’s Mars rover Curiosity on Sol 4302 — Martian day 4,302 of the Mars Science Laboratory mission — on Sept. 12, 2024, at 09:20:51 UTC. NASA/JPL-Caltech Earth planning date: Friday, Sept. 13, 2024
Today, I need to talk about ChemCam, our laser and imaging instrument on the top of Curiosity’s mast. It one of the instruments in the “head” that gives Curiosity that cute look as if it were looking around tilting its head down to the rocks at the rover’s wheels. On Monday, 19th August the ChemCam team at CNES in France planned the 1 millionth shot and Curiosity executed it on the target Royce Lake on sol 4281 on Mars. Even as an Earth scientist used to really big numbers, this is a huge number that took me a while to fully comprehend. 1 000 000 shots! Congratulations, ChemCam, our champion for getting chemistry from a distance – and high-resolution images, too. If you are now curious how Curiosity’s ChemCam instrument works, here is the NASA fact sheet. And, of course, the team is celebrating, which is expressed by those two press releases, one from CNES in France and one from Los Alamos National Laboratory, the two institutions who collaborated to develop and build ChemCam and are now running the instrument for over 12 years! And the PI, Dr Nina Lanza from Los Alamos informs me that the first milestone – 10000 shots was reached as early as Sol 42, which was the sol the DAN instrument used its active mode for the first time. But before I am getting melancholic, let’s talk about today’s plan!
The drive ended fairly high up in the terrain, and that means we see a lot of the interesting features in the channel and generally around us. So, we are on a spot a human hiker would probably put the backpack down, take the water bottle out and sit down with a snack to enjoy the view from a nice high point in the landscape. Well, no such pleasures for Curiosity – and I am pretty sure sugar, which we humans love so much, wouldn’t be appreciated by rover gears anyway. So, let’s just take in the views! And that keeps Mastcam busy taking full advantage of our current vantage point. We have a terrain with lots of variety in front of us, blocks, boulders, flatter areas and the walls are layered, beautiful geology. Overall there are 11 Mastcam observations in the plan adding up to just about 100 individual frames, not counting those taken in the context of atmospheric observations, which are of course also in the plan. The biggest mosaics are on the targets “Western Deposit,” “Balloon Dome,” and “Coral Meadow.” Some smaller documentation images are on the targets “Wales Lake,” “Gnat Meadow,” and “Pig Chute.”
ChemCam didn’t have long to dwell on its milestone, as it’s busy again today. Of course, it will join Mastcam in taking advantage of our vantage point, taking three remote micro imager images on the landscape around us. LIBS chemistry investigations are targeting “Wales Lake,” “Gnat Meadow,” and “Pig Chute.” APXS is investigating two targets, “College Rock” and “Wales Lake,” which will also come with MAHLI documentation. With all those investigations together, we’ll be able to document the chemistry of many targets around us. There is such a rich variety of dark and light toned rocks, and with so much variety everywhere, it’s hard to choose and the team is excited about the three targeted sols … and planning over 4 hours of science over the weekend!
The next drive is planned to go to an area where there is a step in the landscape. Geologists love those steps as they give insights into the layers below the immediate surface. If you have read the word ‘outcrop’ here, then that’s what that means: access to below the surface. But there are also other interesting features in the area, hence we will certainly have an interesting workspace to look at! But getting there will not be easy as the terrain is very complex, so we cannot do it in just one drive. I think there is a rule of thumb here: the more excited the geo-team gets, the more skills our drivers need. Geologists just love rocks, but of course, no one likes driving offroad in a really rocky terrain – no roads on Mars. And right now, our excellent engineers have an extra complication to think about: they need to take extra care where and how to park so Curiosity can actually communicate with Earth. Why? Well, we are in a canyon, and those of you liking to hike, know what canyons mean for cell phone signals… yes, there isn’t much coverage, and that’s the same for Curiosity’s antenna. This new NASA video has more information and insights into the planning room, too! So, we’ll drive halfway to where we want to be but I am sure there will be interesting targets in the new workspace, the area is just so, so complex, fascinating and rich!
And that’s after Mars for you, after 12 years, 42 drill holes, and now 1 Million ChemCam shots. Go Curiosity go!!!
Written by Susanne Schwenzer, Planetary Geologist at The Open University
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Last Updated Sep 13, 2024 Related Terms
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Hubble Examines a Spiral Star Factory
This NASA/ESA Hubble Space Telescope image features the spiral galaxy NGC 5668. ESA/Hubble & NASA, C. Kilpatrick This NASA/ESA Hubble Space Telescope image features a spiral galaxy in the constellation Virgo named NGC 5668. It is relatively near to us at 90 million light-years from Earth and quite accessible for astronomers to study with both space- and ground-based telescopes. At first glance, it doesn’t seem like a remarkable galaxy. It is around 90,000 light-years across, similar in size and mass to our own Milky Way galaxy, and its nearly face-on orientation shows open spiral arms made of cloudy, irregular patches.
One noticeable difference between the Milky Way galaxy and NGC 5668 is that this galaxy is forming new stars 60% more quickly. Astronomers have identified two main drivers of star formation in NGC 5668. Firstly, this high-quality Hubble view reveals a bar at the galaxy’s center, though it might look more like a slight oval shape than a real bar. The bar appears to have affected the galaxy’s star formation rate, as central bars do in many spiral galaxies. Secondly, astronomers tracked high-velocity clouds of hydrogen gas moving vertically between the disk of the galaxy and the spherical, faint halo which surrounds it. These movements may be the result of strong stellar winds from hot, massive stars, that would contribute gas to new star-forming regions.
The enhanced star formation rate in NGC 5668 comes with a corresponding abundance of supernova explosions. Astronomers have spotted three in the galaxy, in 1952, 1954, and 2004. In this image, Hubble examined the surroundings of the Type II SN 2004G, seeking to study the kinds of stars that end their lives as this kind of supernova.
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Last Updated Sep 12, 2024 Editor Andrea Gianopoulos Location NASA Goddard Space Flight Center Related Terms
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Preparations for Next Moonwalk Simulations Underway (and Underwater)
Tests on Earth appear to confirm how the Red Planet’s spider-shaped geologic formations are carved by carbon dioxide.
Spider-shaped features called araneiform terrain are found in the southern hemisphere of Mars, carved into the landscape by carbon dioxide gas. This 2009 image taken by NASA’s Mars Reconnaissance Orbiter shows several of these distinctive formations within an area three-quarters of a mile (1.2 kilometers) wide. NASA/JPL-Caltech/University of Arizona Dark splotches seen in this example of araneiform terrain captured by NASA’s Mars Reconnaissance Orbiter in 2018 are believed to be soil ejected from the surface by carbon dioxide gas plumes. A set of experiments at JPL has sought to re-create these spider-like formations in a lab. NASA/JPL-Caltech/University of Arizona Since discovering them in 2003 via images from orbiters, scientists have marveled at spider-like shapes sprawled across the southern hemisphere of Mars. No one is entirely sure how these geologic features are created. Each branched formation can stretch more than a half-mile (1 kilometer) from end to end and include hundreds of spindly “legs.” Called araneiform terrain, these features are often found in clusters, giving the surface a wrinkled appearance.
The leading theory is that the spiders are created by processes involving carbon dioxide ice, which doesn’t occur naturally on Earth. Thanks to experiments detailed in a new paper published in The Planetary Science Journal, scientists have, for the first time, re-created those formation processes in simulated Martian temperatures and air pressure.
Here’s a look inside of JPL’s DUSTIE, a wine barrel-size chamber used to simulate the temperatures and air pressure of other planets – in this case, the carbon dioxide ice found on Mars’ south pole. Experiments conducted in the chamber confirmed how Martian formations known as “spiders” are created.NASA/JPL-Caltech “The spiders are strange, beautiful geologic features in their own right,” said Lauren Mc Keown of NASA’s Jet Propulsion Laboratory in Southern California. “These experiments will help tune our models for how they form.”
The study confirms several formation processes described by what’s called the Kieffer model: Sunlight heats the soil when it shines through transparent slabs of carbon dioxide ice that built up on the Martian surface each winter. Being darker than the ice above it, the soil absorbs the heat and causes the ice closest to it to turn directly into carbon dioxide gas — without turning to liquid first — in a process called sublimation (the same process that sends clouds of “smoke” billowing up from dry ice). As the gas builds in pressure, the Martian ice cracks, allowing the gas to escape. As it seeps upward, the gas takes with it a stream of dark dust and sand from the soil that lands on the surface of the ice.
When winter turns to spring and the remaining ice sublimates, according to the theory, the spiderlike scars from those small eruptions are what’s left behind.
These formations similar to the Red Planet’s “spiders” appeared within Martian soil simulant during experiments in JPL’s DUSTIE chamber. Carbon dioxide ice frozen within the simulant was warmed by a heater below, turning it back into gas that eventually cracked through the frozen top layer and formed a plume.NASA/JPL-Caltech Re-Creating Mars in the Lab
For Mc Keown and her co-authors, the hardest part of conducting these experiments was re-creating conditions found on the Martian polar surface: extremely low air pressure and temperatures as low as minus 301 degrees Fahrenheit (minus 185 degrees Celsius). To do that, Mc Keown used a liquid-nitrogen-cooled test chamber at JPL, the Dirty Under-vacuum Simulation Testbed for Icy Environments, or DUSTIE.
“I love DUSTIE. It’s historic,” Mc Keown said, noting that the wine barrel-size chamber was used to test a prototype of a rasping tool designed for NASA’s Mars Phoenix lander. The tool was used to break water ice, which the spacecraft scooped up and analyzed near the planet’s north pole.
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This video shows Martian soil simulant erupting in a plume during a JPL lab experiment that was designed to replicate the process believed to form Martian features called “spiders.” When a researcher who had tried for years to re-create these conditions spotted this plume, she was ecstatic. NASA/JPL-Caltech For this experiment, the researchers chilled Martian soil simulant in a container submerged within a liquid nitrogen bath. They placed it in the DUSTIE chamber, where the air pressure was reduced to be similar to that of Mars’ southern hemisphere. Carbon dioxide gas then flowed into the chamber and condensed from gas to ice over the course of three to five hours. It took many tries before Mc Keown found just the right conditions for the ice to become thick and translucent enough for the experiments to work.
Once they got ice with the right properties, they placed a heater inside the chamber below the simulant to warm it up and crack the ice. Mc Keown was ecstatic when she finally saw a plume of carbon dioxide gas erupting from within the powdery simulant.
“It was late on a Friday evening and the lab manager burst in after hearing me shrieking,” said Mc Keown, who had been working to make a plume like this for five years. “She thought there had been an accident.”
The dark plumes opened holes in the simulant as they streamed out, spewing simulant for as long as 10 minutes before all the pressurized gas was expelled.
The experiments included a surprise that wasn’t reflected in the Kieffer model: Ice formed between the grains of the simulant, then cracked it open. This alternative process might explain why spiders have a more “cracked” appearance. Whether this happens or not seems dependent on the size of soil grains and how embedded water ice is underground.
“It’s one of those details that show that nature is a little messier than the textbook image,” said Serina Diniega of JPL, a co-author of the paper.
What’s Next for Plume Testing
Now that the conditions have been found for plumes to form, the next step is to try the same experiments with simulated sunlight from above, rather than using a heater below. That could help scientists narrow down the range of conditions under which the plumes and ejection of soil might occur.
There are still many questions about the spiders that can’t be answered in a lab. Why have they formed in some places on Mars but not others? Since they appear to result from seasonal changes that are still occurring, why don’t they seem to be growing in number or size over time? It’s possible that they’re left over from long ago, when the climate was different on Mars— and could therefore provide a unique window into the planet’s past.
For the time being, lab experiments will be as close to the spiders as scientists can get. Both the Curiosity and Perseverance rovers are exploring the Red Planet far from the southern hemisphere, which is where these formations appear (and where no spacecraft has ever landed). The Phoenix mission, which landed in the northern hemisphere, lasted only a few months before succumbing to the intense polar cold and limited sunlight.
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Andrew Good
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Karen Fox / Molly Wasser
Headquarters, Washington
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Last Updated Sep 11, 2024 Related Terms
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