The
Ingenuity Helicopter
will be deployed from the
Perseverance Rover
for a 30-sol experimental campaign shortly after the rover lands and is commissioned. We describe the helicopter and the ...associated
Technology Demonstration
experiment it will conduct, as well as its role in informing future helicopter missions to Mars. This helicopter will demonstrate, for the first time, autonomous controlled flight of an aircraft in the Mars environment, thus opening up an aerial dimension to Mars exploration. The
1.8
kg
,
1.2
m
diameter helicopter, with twin rotors in a counter-rotating co-axial configuration, will help validate aerodynamics, control, navigation and operations concepts for flight in the thin Martian atmosphere. The rover supports a radio link between the helicopter and mission operators on Earth, and information returned from a planned set of five flights, each lasting up to 90 seconds, will inform the development of new Mars helicopter designs for future missions. Such designs in the
4
kg
–
30
kg
range would have the capability to fly many kilometers daily and carry science payloads of
1
kg
–
5
kg
. Small helicopters can be deployed as scouts for future rovers helping to select interesting science targets, determine optimal rover driving routes, and providing contextual high-vantage imagery. Larger craft can be operated in standalone fashion with a tailored complement of science instruments with direct-to-orbiter communication enabling wide-area operations. Other roles including working cooperatively with a central lander to provide area-wide sampling and science investigations. For future human exploration at Mars, helicopter can be employed to provide reconnaissance.
The SEIS (Seismic Experiment for Interior Structure) instrument onboard the InSight mission will be the first seismometer directly deployed on the surface of Mars. From studies on the Earth and the ...Moon, it is well known that site amplification in low-velocity sediments on top of more competent rocks has a strong influence on seismic signals, but can also be used to constrain the subsurface structure. Here we simulate ambient vibration wavefields in a model of the shallow sub-surface at the InSight landing site in Elysium Planitia and demonstrate how the high-frequency Rayleigh wave ellipticity can be extracted from these data and inverted for shallow structure. We find that, depending on model parameters, higher mode ellipticity information can be extracted from single-station data, which significantly reduces uncertainties in inversion. Though the data are most sensitive to properties of the upper-most layer and show a strong trade-off between layer depth and velocity, it is possible to estimate the velocity and thickness of the sub-regolith layer by using reasonable constraints on regolith properties. Model parameters are best constrained if either higher mode data can be used or additional constraints on regolith properties from seismic analysis of the hammer strokes of InSight’s heat flow probe HP
3
are available. In addition, the Rayleigh wave ellipticity can distinguish between models with a constant regolith velocity and models with a velocity increase in the regolith, information which is difficult to obtain otherwise.
Water ice in the Martian mid‐latitudes has advanced and retreated in response to variations in the planet's orbit, obliquity, and climate. A 150 m‐diameter new impact crater near 35°N provides the ...lowest‐latitude impact exposure of subsurface ice on Mars. This is the largest known ice‐exposing crater and provides key constraints on Martian climate history. This crater indicates a regional, relatively pure ice deposit that is unstable and has nearly vanished. In the past, this deposit may have been tens of meters thick and extended equatorward of 35°N. We infer that it is overlain by pore ice emplaced during temporary stable intervals, due to recent climate variability. The marginal survival of ice here suggests that it is near the edge of shallow ice that regularly exchanges with the atmosphere.
Plain Language Summary
A 150 m‐diameter new impact crater on Mars exposes water ice, constraining the nature of past and present ice sheets and paleoclimate. The past climate has varied, gradually removing a massive ice deposit that has nearly been lost at 35°N but survives at higher latitude.
Key Points
Water ice is exposed in a 150 m‐diameter new impact crater near 35°N on Mars
The ice includes both massive ice and a covering layer of pore ice
This ice marks the southern margin of remaining ice deposits from high‐obliquity periods
The Rotation and Interior Structure Experiment (RISE) on-board the InSight mission will use the lander’s X-band (8 GHz) radio system in combination with tracking stations of the NASA Deep Space ...Network (DSN) to determine the rotation of Mars. RISE will measure the nutation of the Martian spin axis, detecting for the first time the effect of the liquid core of Mars and providing in turn new constraints on the core radius and density. RISE will also measure changes in the rotation rate of Mars on seasonal time-scales thereby constraining the atmospheric angular momentum budget. Finally, RISE will provide a superb tie between the cartographic and inertial reference frames. This paper describes the RISE scientific objectives and measurements, and provides the expected results of the experiment.
Areally extensive exposures of intact olivine/pyroxene‐enriched rock, as well as feldspar‐enriched rock, are found in isolated locations throughout the Martian highlands. The petrogenetic origin(s) ...of these rock units are not well understood, but some previous studies favored an effusive volcanic origin partly on the basis of distinctive composition and relatively high thermal inertia. Here we show that the regolith development, crater retention, and morphological characteristics for many of these “bedrock plains” are not consistent with competent lavas and reinterpret the high thermal inertia orbital signatures to represent friable materials that are more easily kept free of comminution products through eolian activity. Candidate origins include pyroclastic rocks, impact‐generated materials, or detrital sedimentary rocks. Olivine/pyroxene enrichments in bedrock plains relative to surrounding materials could have potentially formed through deflation and preferential removal of plagioclase.
Plain Language Summary
The Martian surface is dominated by loose dust, sands, and rocks, but high spatial resolution imaging has permitted the detection of numerous flat‐lying exposures of ancient, intact bedrock. These “bedrock plains” have previously been interpreted as lava sequences, perhaps similar to lava plains found in the dark parts of the lunar nearside. Here we show evidence that bedrock plains may instead be composed of sedimentary rocks, airfall volcanic ash, or impact‐generated airfall materials. First, the bedrock plains should have developed a thick regolith over time, due to repeated pummeling by impactors over billions of years. But they lack a regolith, suggesting that they break up easily into fine particles that are then easily moved away from the bedrock by wind. Second, the bedrock plains show morphologies that are similar to wind‐eroded soft rocks on Earth. Third, the bedrock plains have fewer small craters than adjacent surfaces, likely due to the relative ease in which craters can be erased through erosion. Bedrock plains are found at all of the proposed landing sites for the upcoming Mars2020 rover; nonlava origins of these rocks should be considered. Direct analysis of these rocks will provide insight into the origin(s) of these globally important materials.
Key Points
Many bedrock plains are likely composed of mechanically weak rocks
Potential origins include lithified detrital sediments, pyroclastics, or impact‐generated materials
High thermal inertia may indicate relatively friable rocks, due to ease of comminution product removal and exposure of lithified surface
The process of identifying the landing site for NASA's Mars 2020 rover began in 2013 by defining threshold mission science criteria related to seeking signs of ancient habitable conditions, searching ...for biosignatures of past microbial life, assembling a returnable cache of samples for possible future return to Earth, and collecting data for planning eventual human missions to the surface of Mars. Mission engineering constraints on elevation and latitude were used to identify candidate landing sites that addressed the scientific objectives of the mission. However, for the first time these constraints did not have a major influence on the viability of candidate sites and, with the new entry, descent, and landing capabilities included in the baseline mission, the vast majority of sites were evaluated and down-selected on the basis of science merit. More than 30 candidate sites with likely acceptable surface and atmospheric conditions were considered at a series of open workshops in the years leading up to the launch. During that period, iteration between engineering constraints and the evolving relative science potential of candidate sites led to the identification of three final candidate sites: Jezero crater (18.4386°N, 77.5031°E), northeast (NE) Syrtis (17.8899°N,77.1599°E) and Columbia Hills (14.5478°S, 175.6255°E). The final landing site will be selected by NASA's Associate Administrator for the Science Mission Directorate. This paper serves as a record of landing site selection activities related primarily to science, an inventory of the number and variety of sites proposed, and a summary of the science potential of the highest-ranking sites.
•Describes the science process for selecting the Mars 2020 rover landing site.•Down selection based on science merit rather than engineering constraints.•Over 30 candidate sites were narrowed to 3 finalists over three workshops.•Final candidate sites include Columbia Hills, Jezero crater, and NE Syrtis.
Atmospheric Science with InSight Spiga, Aymeric; Banfield, Don; Teanby, Nicholas A. ...
Space science reviews,
10/2018, Letnik:
214, Številka:
7
Journal Article
Recenzirano
Odprti dostop
In November 2018, for the first time a dedicated geophysical station, the InSight lander, will be deployed on the surface of Mars. Along with the two main geophysical packages, the Seismic Experiment ...for Interior Structure (SEIS) and the Heat-Flow and Physical Properties Package (HP
3
), the InSight lander holds a highly sensitive pressure sensor (PS) and the Temperature and Winds for InSight (TWINS) instrument, both of which (along with the InSight FluxGate (IFG) Magnetometer) form the Auxiliary Sensor Payload Suite (APSS). Associated with the RADiometer (RAD) instrument which will measure the surface brightness temperature, and the Instrument Deployment Camera (IDC) which will be used to quantify atmospheric opacity, this will make InSight capable to act as a meteorological station at the surface of Mars. While probing the internal structure of Mars is the primary scientific goal of the mission, atmospheric science remains a key science objective for InSight. InSight has the potential to provide a more continuous and higher-frequency record of pressure, air temperature and winds at the surface of Mars than previous
in situ
missions. In the paper, key results from multiscale meteorological modeling, from Global Climate Models to Large-Eddy Simulations, are described as a reference for future studies based on the InSight measurements during operations. We summarize the capabilities of InSight for atmospheric observations, from profiling during Entry, Descent and Landing to surface measurements (pressure, temperature, winds, angular momentum), and the plans for how InSight’s sensors will be used during operations, as well as possible synergies with orbital observations. In a dedicated section, we describe the seismic impact of atmospheric phenomena (from the point of view of both “noise” to be decorrelated from the seismic signal and “signal” to provide information on atmospheric processes). We discuss in this framework Planetary Boundary Layer turbulence, with a focus on convective vortices and dust devils, gravity waves (with idealized modeling), and large-scale circulations. Our paper also presents possible new, exploratory, studies with the InSight instrumentation: surface layer scaling and exploration of the Monin-Obukhov model, aeolian surface changes and saltation / lifing studies, and monitoring of secular pressure changes. The InSight mission will be instrumental in broadening the knowledge of the Martian atmosphere, with a unique set of measurements from the surface of Mars.
A secondary objective for the Perseverance rover mission to Jezero crater, Mars, is to collect igneous rocks for analysis on Earth. The mafic crater floor unit (MFU) represents the best candidate. ...Ten‐meter‐scale craters on the MFU exhibit rocky ejecta, rims, and slopes that indicate resistant rock. The frequency distribution of these craters is, however, low. Comparisons of MFU craters to craters on a lava plain at the Interior Exploration using Seismic Investigation, Geodesy and Heat Transport mission (InSight) landing site reveal that the MFU lacks a granular regolith. Removal of regolith or exhumation of the MFU explains the rocky crater morphology and low density. Erosion rates, calculated using crater retention timescales of ~2.0 Ga for both locations, are 10−3 to 10−4 m/Myr. The rates derive from craters impacted into rocky materials on the MFU versus regolith at InSight. The difference in material strength, yet comparable erosion rates, requires more vigorous surface processes at Jezero relative to global averages on Mars.
Plain Language Summary
Jezero crater is a 45‐km diameter impact crater on Mars. It contains a river delta and deposits that suggest that it was once filled by a lake. Jezero is the landing site for NASA's Mars Perseverance rover, scheduled to land in February 2021. A primary objective of the rover is to sample rocks to determine if Mars was once habitable for life. A secondary objective is to obtain igneous rocks, or rocks that crystallize from magma or lava. Igneous rocks can be used to provide absolute age constraints on the rocks that they surround or are contained within. The purpose of this study is to evaluate a geologic unit called the mafic floor unit that is the best candidate for sampling igneous material. Small craters that formed from meteor impacts in the floor unit are surrounded by large rocks that suggest that the material is resistant to weathering and erosion, consistent with craters impacted into hard igneous rocks or other competent material. However, the unit lacks a sand‐sized surface soil that is typical of most lava plains on Mars. Comparisons to the InSight landing site indicate that wind may be responsible for removing sandy material and exposing rock.
Key Points
The mafic floor unit at Jezero crater is a morphologically resistant unit
The mafic floor unit at Jezero crater lacks a granular surface regolith like other lava plains on Mars
Surface processes operate at relatively higher rates within Jezero crater compared to global averages on Mars
•Basalt rocks transported or affected by different geologic processes were analyzed.•Most basaltic rocks are disc or sphere shaped due to cooling fractures.•Angularity (roundness) is the most ...diagnostic morphometric index.•Size frequency distributions are controlled by the initial fracture and fragmentation.•Our results support interpretations of rock populations at different landing sites.
We analyzed the morphometry of basaltic rock populations that have been emplaced or affected by a variety of geologic processes, including explosive volcanic eruptions (as a proxy for impact cratering), catastrophic flooding, frost shattering, salt weathering, alluvial deposition, and chemical weathering. Morphometric indices for these rock populations were compared to an unmodified population of rocks that had broken off a solidified lava flow to understand how different geologic processes change rock shape. We found that a majority of rocks have an sphericity described as either a disc or sphere in the Zingg classification system and posit that this is a function of cooling fractures in the basalt (Zingg 1935 Schweiz. Miner. Petrogr. Mitt., 15, 39–140). Angularity (roundness) is the most diagnostic morphometric index, but the Corey Shape Factor (CSF), Oblate–Prolate Index (OPI) and deviation from compactness (D) also sometimes distinguished weathering processes. Comparison of our results to prior analyses of rock populations found at the Mars Pathfinder, Spirit, and Curiosity landing sites support previous conclusions. The observation that the size-frequency distribution of terrestrial rock populations follow exponential functions similar to lander and orbital measurements of rocks on Mars, which is expected from fracture and fragmentation theory, indicates that these distributions are being dominantly controlled by the initial fracture and fragmentation of the basalt.
A 10-km diameter crater named Zunil in the Cerberus Plains of Mars created
∼
10
7
secondary craters 10 to 200 m in diameter. Many of these secondary craters are concentrated in radial streaks that ...extend up to 1600 km from the primary crater, identical to lunar rays. Most of the larger Zunil secondaries are distinctive in both visible and thermal infrared imaging. MOC images of the secondary craters show sharp rims and bright ejecta and rays, but the craters are shallow and often noncircular, as expected for relatively low-velocity impacts. About 80% of the impact craters superimposed over the youngest surfaces in the Cerberus Plains, such as Athabasca Valles, have the distinctive characteristics of Zunil secondaries. We have not identified any other large (⩾10 km diameter) impact crater on Mars with such distinctive rays of young secondary craters, so the age of the crater may be less than a few Ma. Zunil formed in the apparently youngest (least cratered) large-scale lava plains on Mars, and may be an excellent example of how spallation of a competent surface layer can produce high-velocity ejecta (Melosh, 1984, Impact ejection, spallation, and the origin of meteorites, Icarus 59, 234–260). It could be the source crater for some of the basaltic shergottites, consistent with their crystallization and ejection ages, composition, and the fact that Zunil produced abundant high-velocity ejecta fragments. A 3D hydrodynamic simulation of the impact event produced 10
10 rock fragments ⩾10 cm diameter, leading to up to 10
9 secondary craters ⩾10 m diameter. Nearly all of the simulated secondary craters larger than 50 m are within 800 km of the impact site but the more abundant smaller (10–50 m) craters extend out to 3500 km. If Zunil is representative of large impact events on Mars, then secondaries should be more abundant than primaries at diameters a factor of ∼1000 smaller than that of the largest primary crater that contributed secondaries. As a result, most small craters on Mars could be secondaries. Depth/diameter ratios of 1300 small craters (10–500 m diameter) in Isidis Planitia and Gusev crater have a mean value of 0.08; the freshest of these craters give a ratio of 0.11, identical to that of fresh secondary craters on the Moon (Pike and Wilhelms, 1978, Secondary-impact craters on the Moon: topographic form and geologic process, Lunar Planet. Sci. IX, 907–909) and significantly less than the value of ∼0.2 or more expected for fresh primary craters of this size range. Several observations suggest that the production functions of Hartmann and Neukum (2001, Cratering chronology and the evolution of Mars, Space Sci. Rev. 96, 165–194) predict too many primary craters smaller than a few hundred meters in diameter. Fewer small, high-velocity impacts may explain why there appears to be little impact regolith over Amazonian terrains. Martian terrains dated by small craters could be older than reported in recent publications.
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