Linear Ion Entice Mass Spectrometer (LITMS)
To deal with the rising want for in situ molecular evaluation of Mars samples at superb spatial scales, NASA is creating the miniature LITMS instrument, which mixes a laser and fuel chromatograph mass spectrometer with a precision subsampling system. LITMS executes a strong seek for biosignatures and geochemical gradients in a rock pattern’s particular person layers the place such options are most distinct.
Staff members (left to proper) Samuel Larson, Marco Castillo, and Andrej Grubisic making ready to research a Mars analog soil pattern with laser desorption/ionization within the flight-like LITMS instrument within the Planetary Environments Laboratory at Goddard Area Flight Heart.
Mars continues to entrance and problem us as a world without delay strikingly Earth-like, and but clearly alien upon nearer investigation. Tantalizing proof of an early water-rich period and the potential for subsurface preservation have made the prospect of detecting historic and even fashionable indicators of life a central focus of Mars exploration. A sequence of highly effective orbiting and floor missions over the previous few many years has vastly enriched our understanding of Mars as a fancy, dynamic planet, with choose areas exhibiting proof of getting been liveable previously.
These missions have culminated most lately within the arrival of the Perseverance rover, which is each exploring for potential signatures of previous life and amassing high-value samples for later evaluation in Earth labs through Mars Pattern Return (MSR). The MSR samples will deliver unprecedented depth to our investigation of the geochemistry, habitability, and presumably the biology of Mars, enabled by the ultra-sensitive and micron-scale probes afforded by terrestrial laboratories. Together with new information, MSR can even inevitably invite new questions and encourage continued future exploration, probably with a finer scientific focus.
Future robotic missions to look at potential niches for the preservation of biosignatures will undoubtedly name for extra intensive research of the molecular composition of samples at superb spatial scales. Martian rock samples are heterogeneous on millimeter and submillimeter scales, reflecting the merging of varied mineral phases of differing origins throughout rock formation or the deposition of skinny sedimentary layers. Moreover, natural compounds which will solely happen in hint quantities within the bulk rock, and thus are exhausting to detect within the presence of excessive background noise, could also be discovered at a lot greater concentrations in remoted phases or layers. As on Earth, such layers can be most evident in a drill core pattern, the place even “quick” (few-cm) intact cores can file dramatic chemical variations with depth.
Devices that carry out superb (submillimeter) scale evaluation of rock samples are presently deployed on the Perseverance rover. These key investigations allow in situ science in addition to establish samples for return to Earth. Wanting ahead, the necessity for detailed molecular characterization at such scales, with the total analytical toolkit of a multi-source mass spectrometer, will develop. Scientists will wish to distinguish potential biosignatures resembling advanced natural compounds or homochirality – life’s choice for utilizing solely right- or left-handed types of sure chiral molecules. To this finish, an SMD-sponsored group based mostly at Goddard Area Flight Heart has been creating the Linear Ion Entice Mass Spectrometer (LITMS) instrument for precision molecular evaluation on a future Mars astrobiology lander or rover.
LITMS is an enhanced model of the Mars Natural Molecule Analyzer (MOMA) mass spectrometer that may launch on the ExoMars rover mission in 2022. Like MOMA, LITMS incorporates each fuel chromatograph mass spectrometry (GCMS) and laser desorption mass spectrometry (LDMS) modes to allow investigation of a variety of compounds. However LITMS analyzes an expanded set of compounds with greater precision, by means of enhancements resembling the flexibility to detect a wider vary of molecular weights and the potential to research unfavourable polarity ions along with the optimistic ion spectra MOMA can analyze. LITMS additionally incorporates a precision sampling system that enables a rock core pattern to be interrogated by each a superb grinding software (for GCMS) and a centered laser (for LDMS), offering complementary molecular analyses from submillimeter-scale factors on the core.
A conceptual schematic of LITMS as configured for a mission is proven beneath. The linear ion entice analyzer is contained within the mass spectrometer (MS) Housing, which is mounted to a rover/lander interface plate. The radio frequency (RF) Tank supplies the oscillating voltage to the electrodes that entice and eject ions.
An outline of LITMS because it prepares to research a core pattern, obtained by a Coring Drill on a 5-degree of freedom (5-DOF) robotic arm, utilizing laser desorption/ionization (LDI). Notional drill and arm elements, not a part of the LITMS instrument, are depicted in darkish coloration on the appropriate.
Within the determine above, LITMS is interfaced to a robotic arm that has positioned an acquired drill core (nominally 8 mm diameter and a number of other cm lengthy) beneath the MS. The core is held in a PreView Bit (developed by NASA’s companions at Honeybee Robotics), which comprises a slot to allow viewing and evaluation of the core (which will have layers as pictured). Within the depicted place, any level on the uncovered core will be sampled by the pulsed ultraviolet (UV) laser, forming ions which are ingested immediately by means of the Aperture Valve and a slender tube into the MS. The laser focal spot is simply a fraction of a mm in diameter and permits exact maps to be generated by slowly shifting the core. In a second retracted place above the Precision Core Sampler, a skinny grinding wheel is pressed gently on the core to generate just a few milligrams of powder that falls by means of a funnel right into a small cylindrical oven (not proven within the determine). The oven might then be sealed and heated to create fuel from the powder pattern for evaluation by GCMS. This sequence permits the LDMS evaluation, which is actually non-destructive, to establish high-priority factors on the core for GCMS evaluation, offering a strong “one-two punch” to detect hint molecules hidden in a single core layer.
With help from NASA’s Maturation of Devices for Photo voltaic System Exploration (MatISSE) Program, the Goddard group has developed a prototype of LITMS with the identical measurement, form, capabilities, and management system as a flight instrument. This mannequin, proven within the picture beneath, can interface each with the robotic arm and Preview Bit system (not proven) in addition to a rotating pattern cup carousel (as within the picture) to permit loading of powdered samples for testing and discipline deployment. For laboratory and discipline testing a small industrial off-the shelf (COTS) Ultraviolet (UV) laser is used rather than the distinctive flight prototype laser.
LITMS prototype instrument in laboratory configuration for laser evaluation of strong samples loaded into metallic cups. Inset: Different laser evaluation of rock drill core pattern within the Preview Bit.
The determine inset reveals a closeup picture of the underside of the ion inlet tube (with Aperture Valve) simply above a Mars analog rock core (a rock pattern much like these discovered on Mars) held in place by the Preview Bit. Optical emission from the UV laser is seen on the core floor immediately underneath the inlet.
In the course of the MatISSE-sponsored challenge, the LITMS prototype (together with MS, flight-like electronics, and precision sampler) was designed, assembled, and examined within the laboratory utilizing a spread of “customary” samples (these with identified compositions designed to test instrument efficiency) in addition to a number of pure Mars analogs, together with some comparable in composition to rocks noticed on earlier Mars missions. Throughout lab testing, the group found that in soils containing perchlorate (an inorganic chemical discovered on Mars) LITMS was capable of detect the particular perchlorate anion and establish its metallic heart (e.g., Mg or Ca) whereas concurrently detecting high-molecular-weight fragrant natural compounds utilizing LDMS. Moreover, LITMS confirmed nice promise for the detection of organics that might be related to organic matter remoted in skinny layers or small mineral phases.
ATACAMA FIELD CAMPAIGN
The flight-like design of LITMS permits it to be configured in a extremely compact kind for discipline testing, permitting for the evaluation of natural and inorganic molecules in Earth environments underneath chosen operational constraints to simulate these of a flight mission. These capabilities had been demonstrated in a preliminary discipline marketing campaign within the Atacama Desert, Chile, in March 2019 as a part of the Atacama Rover Astrobiology Drilling Research (ARADS) challenge, led by Dr. Brian Glass of NASA Ames Analysis Heart and supported by means of the NASA Planetary Science and Know-how from Analog Analysis (PSTAR) Program.
For the ARADS marketing campaign, important repackaging of the laboratory prototype was accomplished to supply a standalone, environmentally tolerant system. Options of the fieldable LITMS embrace a ruggedized, shock-mounted chassis; a extremely compact implementation of the brassboard electronics modules right into a “mini-crate” analog of the flight foremost electronics field; and a fuel dealing with and pumping system to allow contamination-free user-mounting of samples right into a chamber that simulates the martian atmosphere for which LITMS was designed. ARADS represents one of many first deployments of a flight-like planetary mass spectrometer to a high-fidelity analog discipline web site.
The LITMS discipline prototype delivered to the ARADS discipline web site within the Atacama Desert (left) in March 2019 with instance deep drill gap (inset). The prototype was arrange in situ inside a wind/mud and thermal protecting enclosure (heart). On-site group performing instrument check-out and analog tactical planning (proper).
Whereas within the Atacama, in situ analyses of samples from the floor all the way down to 90 cm depth had been carried out with LITMS. These analyses confirmed considerably various chemical profiles (relative portions of inorganic and natural compounds mirrored as mass spectral peak patterns) with rising depth, which displays the compositional modifications associated to layers of various environmental processing and preservation within the ultra-arid Atacama soil. These preliminary knowledge present extraordinarily helpful enter for short-term “tactical” choices about additional drilling and examination by LITMS and different rover devices. The longer-term “strategic” evaluation carried out after the sector marketing campaign, which is ongoing within the lab at Goddard, is analogous to the method on a mission the place future web site choice and up to date hypotheses consequence from in-depth processing and evaluation of beforehand collected knowledge.
PATH FORWARD FOR LITMS
LITMS is able to proceed to a flight mission to Mars or elsewhere, ought to the chance come up. The group continues to research Atacama and different analog samples to analysis the connection between the analog atmosphere and the characterization of doubtless biogenic organics. Future discipline campaigns to carry out further in situ science and achieve discipline instrument expertise are of excessive curiosity to the LITMS group, notably given the deployment-ready configuration of the instrument.
Within the lab, the LITMS instrument can function a strong software for inspecting analogs of samples that could be discovered at Oxia Planum by the ExoMars rover and analyzed with MOMA in 2023. Whereas MOMA depends on its Testbed Mannequin on Earth to precisely duplicate the habits and efficiency of the flight instrument on Mars, that Testbed Mannequin is primarily a prognosis and verification software and won’t be used for in depth analog pattern analyses to assist science interpretation through the mission.
LITMS, nonetheless, can serve not solely as a performance-traceable useful resource for the MOMA group, however may illuminate pattern properties, resembling the total number of organics current, that could be unclear from MOMA knowledge alone, because of the detection enhancements constructed into LITMS. The LITMS prototype moreover affords a platform to check new analytical protocols that might be applied on MOMA by means of its built-in management software program re-programmability. One instance of that is the optimization of tandem mass spectrometry, or MS/MS, that allows particular person natural compounds to be remoted and their inner buildings studied. LITMS allows MS/MS to be examined extensively on advanced samples to judge its potential utility on Mars.
Lastly, one other helpful end result of the LITMS effort is the design of the spectrometer on the upcoming Dragonfly mission to Saturn’s moon Titan. At present underneath growth, the Dragonfly Mass Spectrometer (DraMS) is a extremely superior linear ion trap-based instrument that options a number of of the brand new capabilities and classes realized from LITMS. NASA expects DraMS to conduct a radical evaluation of the extraordinary and compelling floor composition of Titan.
Dr. William B. Brinckerhoff, NASA Goddard Area Flight Heart
PSD’s Maturation of Devices for Photo voltaic System Exploration (MatISSE) Program, the Goddard Instrument Subject Staff (GIFT), and the Planetary Science and Know-how from Analog Analysis (PSTAR) Program.
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