The unexpected surface of asteroid (101955) Bennu.

NASA'S Origins, Spectral Interpretation, Resource Identification and Security-Regolith Explorer (OSIRIS-REx) spacecraft recently arrived at the near-Earth asteroid (101955) Bennu, a primitive body that represents the objects that may have brought prebiotic molecules and volatiles such as water to Earth1. Bennu is a low-albedo B-type asteroid2 that has been linked to organic-rich hydrated carbonaceous chondrites3. Such meteorites are altered by ejection from their parent body and contaminated by atmospheric entry and terrestrial microbes. Therefore, the primary mission objective is to return a sample of Bennu to Earth that is pristine-that is, not affected by these processes4. The OSIRIS-REx spacecraft carries a sophisticated suite of instruments to characterize Bennu's global properties, support the selection of a sampling site and document that site at a sub-centimetre scale5-11. Here we consider early OSIRIS-REx observations of Bennu to understand how the asteroid's properties compare to pre-encounter expectations and to assess the prospects for sample return. The bulk composition of Bennu appears to be hydrated and volatile-rich, as expected. However, in contrast to pre-encounter modelling of Bennu's thermal inertia12 and radar polarization ratios13-which indicated a generally smooth surface covered by centimetre-scale particles-resolved imaging reveals an unexpected surficial diversity. The albedo, texture, particle size and roughness are beyond the spacecraft design specifications. On the basis of our pre-encounter knowledge, we developed a sampling strategy to target 50-metre-diameter patches of loose regolith with grain sizes smaller than two centimetres4. We observe only a small number of apparently hazard-free regions, of the order of 5 to 20 metres in extent, the sampling of which poses a substantial challenge to mission success.

Bright carbonate veins on asteroid (101955) Bennu: Implications for aqueous alteration history.

The composition of asteroids and their connection to meteorites provide insight into geologic processes that occurred in the early Solar System. We present spectra of the Nightingale crater region on near-Earth asteroid Bennu with a distinct infrared absorption around 3.4 micrometers. Corresponding images of boulders show centimeters-thick, roughly meter-long bright veins. We interpret the veins as being composed of carbonates, similar to those found in aqueously altered carbonaceous chondrite meteorites. If the veins on Bennu are carbonates, fluid flow and hydrothermal deposition on Bennu's parent body would have occurred on kilometer scales for thousands to millions of years. This suggests large-scale, open-system hydrothermal alteration of carbonaceous asteroids in the early Solar System.

Application of TMAH thermochemolysis to the detection of nucleobases: Application to the MOMA and SAM space experiment.

Thermochemolysis of seven nucleobases-adenine, thymine, uracil, cytosine, guanine, xanthine, and hypoxanthine-in tetramethylammonium hydroxide (TMAH) was studied individually by pyrolysis gas chromatography mass spectrometry in the frame of the Mars surface exploration. The analyses were performed under conditions relevant to the Sample Analysis at Mars (SAM) instrument of the Mars Curiosity Rover and the Mars Organic Molecule Analyzer (MOMA) instrument of the ExoMars Rover. The thermochemolysis products of each nucleobase were identified and the reaction mechanisms studied. The thermochemolysis temperature was optimized and the limit of detection and quantification of each nucleobase were also investigated. Results indicate that 600°C is the optimal thermochemolysis temperature for all seven nucleobases. The methylated products trimethyl-adenine, 1, 3-dimethyl-thymine, 1, 3-dimethyl-uracil, trimethyl-cytosine, 1, 3, 7-trimethyl-xanthine (caffeine), and dimethyl-hypoxanthine, respectively, are the most stable forms of adenine, thymine, uracil, cytosine, guanine, and xanthine, and hypoxanthine in TMAH solutions. The limits of detection for adenine, thymine, and uracil were 0.075 nmol; the limits of detection for guanine, cytosine, and hypoxanthine were higher, at 0.40, 0.55, and 0.75 nmol, respectively. These experiments allowed to well constrain the analytical capabilities of the thermochemolysis experiments that will be performed on Mars to detect nucleobases.

Episodes of particle ejection from the surface of the active asteroid (101955) Bennu.

Active asteroids are those that show evidence of ongoing mass loss. We report repeated instances of particle ejection from the surface of (101955) Bennu, demonstrating that it is an active asteroid. The ejection events were imaged by the OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer) spacecraft. For the three largest observed events, we estimated the ejected particle velocities and sizes, event times, source regions, and energies. We also determined the trajectories and photometric properties of several gravitationally bound particles that orbited temporarily in the Bennu environment. We consider multiple hypotheses for the mechanisms that lead to particle ejection for the largest events, including rotational disruption, electrostatic lofting, ice sublimation, phyllosilicate dehydration, meteoroid impacts, thermal stress fracturing, and secondary impacts.

OSIRIS-REx Contamination Control Strategy and Implementation.

OSIRIS-REx will return pristine samples of carbonaceous asteroid Bennu. This article describes how pristine was defined based on expectations of Bennu and on a realistic understanding of what is achievable with a constrained schedule and budget, and how that definition flowed to requirements and implementation. To return a pristine sample, the OSIRIS-REx spacecraft sampling hardware was maintained at level 100 A/2 and <180 ng/cm2 of amino acids and hydrazine on the sampler head through precision cleaning, control of materials, and vigilance. Contamination is further characterized via witness material exposed to the spacecraft assembly and testing environment as well as in space. This characterization provided knowledge of the expected background and will be used in conjunction with archived spacecraft components for comparison with the samples when they are delivered to Earth for analysis. Most of all, the cleanliness of the OSIRIS-REx spacecraft was achieved through communication among scientists, engineers, managers, and technicians.

Organic molecules in the Sheepbed Mudstone, Gale Crater, Mars.

The Sample Analysis at Mars (SAM) instrument on board the Mars Science Laboratory Curiosity rover is designed to conduct inorganic and organic chemical analyses of the atmosphere and the surface regolith and rocks to help evaluate the past and present habitability potential of Mars at Gale Crater. Central to this task is the development of an inventory of any organic molecules present to elucidate processes associated with their origin, diagenesis, concentration, and long-term preservation. This will guide the future search for biosignatures. Here we report the definitive identification of chlorobenzene (150-300 parts per billion by weight (ppbw)) and C2 to C4 dichloroalkanes (up to 70 ppbw) with the SAM gas chromatograph mass spectrometer (GCMS) and detection of chlorobenzene in the direct evolved gas analysis (EGA) mode, in multiple portions of the fines from the Cumberland drill hole in the Sheepbed mudstone at Yellowknife Bay. When combined with GCMS and EGA data from multiple scooped and drilled samples, blank runs, and supporting laboratory analog studies, the elevated levels of chlorobenzene and the dichloroalkanes cannot be solely explained by instrument background sources known to be present in SAM. We conclude that these chlorinated hydrocarbons are the reaction products of Martian chlorine and organic carbon derived from Martian sources (e.g., igneous, hydrothermal, atmospheric, or biological) or exogenous sources such as meteorites, comets, or interplanetary dust particles. KEY POINTS: First in situ evidence of nonterrestrial organics in Martian surface sediments Chlorinated hydrocarbons identified in the Sheepbed mudstone by SAM Organics preserved in sample exposed to ionizing radiation and oxidative condition.

Tongue strength Part I: Following total laryngectomy.

Surgical repositioning of the genioglossus muscle, as in total laryngectomy, may have an adverse effect on the protrusive strength of the tongue. To test this premise, anterior and lateral tongue strength measures were obtained from 10 laryngectomized and 15 normal subjects by means of a pressure transducer and recording device. The results indicated no significant difference between laryngectomized and normal subjects on tongue strength measures. Further, all laryngectomized subjects were judged to have good to excellent esophageal speech. It was concluded that laryngectomy does not adversely affect the major musculature concerned with protrusive tongue strength for proficient esophageal speakers.

Tongue strength. Part II: in artificial alaryngeal speech.

Tongue strength does not appear to be reduced in proficient esophageal speakers. However, no data exist on tongue strength for laryngectomized subjects who have not developed esophageal speech. Anterior and lateral tongue strength measures were obtained from 13 laryngectomized subjects who used an artificial larynx and 15 normal subjects by means of a pressure transducer and recording device. The results indicated that laryngectomized subjects had significantly weaker tongues in two of three directions measured. It was concluded that laryngectomy may affect tongue strength, but that the method of alaryngeal speech utilized postoperatively influences the return to normal.

Videostroboscopy of the pharyngoesophageal segment in total laryngectomees.

OBJECTIVES: The reconstructed pharyngoesophageal segment (PES) serves as the neoglottis following total laryngectomy, as it provides the source of vibration for production of tracheoesophageal puncture (TEP) voice. To date, little information exists regarding the vibratory characteristics of the PES. The purpose of this investigation was to study the anatomy and physiology of the PES using videostroboscopy. STUDY DESIGN: Prospective study investigating the anatomy and physiology of the PES in 34 laryngectomees who used TEP speech as their primary form of communication. MATERIALS AND METHODS: Videostroboscopy and voice recordings were graded by three trained, blinded judges using a seven-point scale. RESULTS: The patients demonstrated differences that allowed for separation of patients into two main groups: "poor" and "effective" TEP speakers. The voice quality differences were explained by anatomic and physiologic characteristics of the PES. Redundant, thick, and dyssynchronous PES features were observed in patients with poor TEP speech skills; the effective speakers exhibited less redundant, thinner mucosa and more synchronous vibratory patterns. Moreover, the latter subgroup consistently demonstrated a greater degree of volitional PES control and less spasmodic activity than their poorly speaking counterparts. Length of the PES opening (measured in the horizontal plane) as well as amount and consistency of secretions did not appear to influence TEP speech or voice proficiency. CONCLUSION: Videostroboscopy in laryngectomees is a noninvasive, inexpensive, easily performed procedure that may contribute valuable information regarding the anatomy and physiology of the PES, especially in patients who experience difficulties achieving satisfactory TEP voice and speech production.

Functional outcomes after supracricoid laryngectomy.

OBJECTIVES: Local control and 5-year survival rates are similar for patients undergoing total laryngectomy and supracricoid laryngectomy for the treatment of advanced-stage laryngeal carcinoma. However, comprehensive studies of functional outcomes after supracricoid laryngectomy are lacking. STUDY DESIGN: Cohort study. METHODS: This investigation provides objective voice laboratory data, skilled listener impressions of voice samples, swallowing evaluations, and patient self-perceptions of speech ability obtained from 10 supracricoid laryngectomees. RESULTS: Results demonstrated variable acoustic and speech aerodynamic disturbances, hoarse-breathy vocal quality, and speech dysfluency. Patients' self-perceptions of voice revealed severe dysphonia that induced certain emotional, physical, and functional setbacks. However, blinded judges rated these individuals as possessing intelligible speech and communication skills. All patients demonstrated premature spillage of the bolus and varying degrees of laryngeal penetration, aspiration, and retention during swallowing studies. However, each patient used a compensatory strategy to protect the airway. Voice and swallowing abilities appeared to depend on the mobility of the arytenoid cartilages, base of tongue action, and residual supraglottic tissue for the creation of a competent neoglottal sphincter complex that vibrated during phonation efforts and protected the airway during deglutition. CONCLUSIONS: Supracricoid laryngectomy avoids the potential complications, limitations, and emotional problems associated with a permanent tracheostoma. All patients demonstrated intelligible voice and effective swallowing function postoperatively, supporting supracricoid laryngectomy as a suitable alternative surgical approach to the total laryngectomy in select patients.

Laryngeal obstructing saccular cysts: a review of this disease and treatment approach emphasizing complete endoscopic carbon dioxide laser excision.

Airway-obstructing saccular cysts in adults are rare laryngeal anomalies. Treatment with tracheotomy may be needed for control of the airway, often followed by marsupialization of the cyst wall. Unfortunately, recurrence rates are high following marsupialization. We describe 2 patients with saccular cysts obstructing the airway and discuss airway management and the results following complete endoscopic carbon dioxide laser excision. Both patients had normal voice and swallowing function postoperatively and are disease free.

A kinetic estimate of the free aldehyde content of aldoses.

The relative free aldehyde content of eight hexoses and four pentoses has been estimated within about 10% from the rate constants for their reaction with urazole (1,2,4-triazole-3,5-dione). These values of the percent free aldehyde are in agreement with those estimated from CD measurements, but are more accurate. The relative free aldehyde contents for the aldoses were then correlated to various literature NMR measurements to obtain the absolute values. This procedure was also done for three deoxyaldoses, which react much more rapidly than can be accounted for by the free aldehyde content. This difference in reactivity between aldoses and deoxyaldoses is due to the inductive effect of the H versus the OH on C-2'. This may help explain why deoxyribonucleosides hydrolyze much more rapidly than ribonucleosides.

Botulinum toxin injection of the cricopharyngeus muscle for the treatment of dysphagia.

OBJECTIVE: This study was conducted to evaluate, subjectively and objectively, the diagnostic and therapeutic effects of botulinum toxin (Botox) in patients with dysphagia caused by cricopharyngeus (CP) muscle spasm and/or hypertonicity. METHODS: A retrospective chart review was done of 5 patients with normally functioning larynges treated with CP Botox injection for dysphagia caused by perceived spasm. Subjective measures of swallowing function after injection were obtained with a patient questionnaire. Objective data were obtained both before and after surgery by one or more of the following tests: modified barium swallow study, manometry, videostroboscopy, and fiberoptic endoscopic evaluation of swallowing. Quality-of-life measures were obtained with a swallowing rating scale. RESULTS: Overall, all patients had initial improvement in swallowing after Botox injection. The duration of benefit was from 2 to 14 months. There were no complications. Four of 5 patients had long-term benefits, as evidenced by decreased or eliminated aspiration symptoms, removal of tracheotomy, ability to eat solid foods, and weight gain. One patient continues to have poor swallowing function. CONCLUSION: Botox injection of the CP muscle to treat dysphagia is effective in patients with underlying muscle spasm or hypertonicity. A positive response to Botox can also help confirm the diagnosis of CP muscle spasm.

Botulinum toxin injection to improve tracheoesophageal speech after total laryngectomy.

Total laryngectomy patients, after undergoing a tracheoesophageal puncture (TEP), may have poor TEP speech because of hypertonicity or spasm of the pharyngoesophageal segment (PES). Conventional treatment options include speech therapy, PES dilation, pharyngeal neurectomy, and myotomy. Botulinum toxin injection into the PES has recently been reported to be effective for this disorder. However, data accumulated were based primarily on subjective analyses. This prospective investigation used both qualitative and quantitative measures to assess the effects of videofluoroscopy-guided botulinum toxin injection on TEP voice quality in laryngectomees with PES dysfunction. Patients underwent voice analyses, tracheal air pressure measures, and barium swallows before and after botulinum toxin injection. Seven of 8 patients had significant voice quality improvement, and tracheal air pressures normalized in 6 of 8 patients after injection. Videofluoroscopic botulinum toxin injection into the PES is efficacious, safe, and cost-effective and should be considered as a first-line therapy for the treatment of laryngectomees with poor quality TEP speech caused by PES dysfunction.

Videostroboscopy of the pharyngoesophageal segment in laryngectomy patients treated with botulinum toxin.

OBJECTIVES: The purpose of this investigation was to use videostroboscopy to study the physiologic and biomechanical effects of botulinum toxin (Botox) injection on the pharyngoesophageal segment (PES) in total laryngectomy patients with poor-quality tracheoesophageal puncture (TEP) voice caused by PES spasm. METHODS: The following was a prospective study. Videostroboscopy of the PES and videotaped recordings of patients performing TEP voice tasks were conducted before and after Botox injection of the PES. Ratings of videostroboscopic and speech samples were performed by 3 blinded judges with extensive experience with this patient population. RESULTS: Perceptually, TEP voice was more fluent and less strained after injection. Videostroboscopically, patients demonstrated improved PES volitional control and mucosal wave characteristics after Botox injection. CONCLUSION: Botox injection in total laryngectomy patients with poor-quality TEP voice caused by PES spasm provides improved physiologic and biomechanical function of the PES, as demonstrated for the first time videostroboscopically. These findings help explain the perceptual ratings of TEP voice improvement noted after Botox injection. Videostroboscopy can be used to provide diagnostic information to help confirm the clinical impression of PES spasm, as well as to document the effects of Botox injection on PES function.

Use of topical lidocaine in the treatment of muscle tension dysphonia.

This investigation explored the potential usefulness of topical lidocaine in the treatment of muscle tension dysphonia. Three patients with this disorder, who were previously unresponsive to standard voice therapy, were treated with lidocaine. In each case, the outcome was prompt, clinically significant, and sustained. Persistently high-pitched and shrill vocal quality was converted to near normal voice patterns within 15 minutes after transcricothyroid membrane lidocaine injection. We suggest that this temporary and simple laryngeal and tracheal anesthetic technique may have helped to break the perverse cycle of hyperactive glottal and supraglottal muscle contractions evident in each of these patients during phonation efforts. We discuss the possible sensorimotor mechanism of action of this therapeutic technique.

Tongue strength and alternate motion rates in normal and dysarthric subjects.

Tongue strength and alternate motion rates were measured in 50 normal subjects and in 18 subjects who had different neuropathologic types of dysarthria. The dysarthric subjects did not differ significantly from one another on any of the test measures. However, as a group they differed significantly from their normal counterparts in that they demonstrated weaker tongue strength, reduced and unsustained levels of maximum tongue strength effort, and slower alternate motion rates. Clinical implications are discussed.

Does aspartic acid racemization constrain the depth limit of the subsurface biosphere?

Previous studies of the subsurface biosphere have deduced average cellular doubling times of hundreds to thousands of years based upon geochemical models. We have directly constrained the in situ average cellular protein turnover or doubling times for metabolically active micro-organisms based on cellular amino acid abundances, D/L values of cellular aspartic acid, and the in vivo aspartic acid racemization rate. Application of this method to planktonic microbial communities collected from deep fractures in South Africa yielded maximum cellular amino acid turnover times of ~89 years for 1 km depth and 27 °C and 1-2 years for 3 km depth and 54 °C. The latter turnover times are much shorter than previously estimated cellular turnover times based upon geochemical arguments. The aspartic acid racemization rate at higher temperatures yields cellular protein doubling times that are consistent with the survival times of hyperthermophilic strains and predicts that at temperatures of 85 °C, cells must replace proteins every couple of days to maintain enzymatic activity. Such a high maintenance requirement may be the principal limit on the abundance of living micro-organisms in the deep, hot subsurface biosphere, as well as a potential limit on their activity. The measurement of the D/L of aspartic acid in biological samples is a potentially powerful tool for deep, fractured continental and oceanic crustal settings where geochemical models of carbon turnover times are poorly constrained. Experimental observations on the racemization rates of aspartic acid in living thermophiles and hyperthermophiles could test this hypothesis. The development of corrections for cell wall peptides and spores will be required, however, to improve the accuracy of these estimates for environmental samples.

Characteristics of frontal lispers clustered according to severity.

The purpose of this investigation was to determine the relationship among frontal lisping, protrusive lingual force, and lingual diadochokinetic rates when subjects are grouped according to severity of lisping. Results revealed that when compared to normal speaking counterparts: (1) lispers in each severity subgroup exhibited significantly weaker protrusive lingual forces and that the significance of such differences increased with the severity of lisping; and (2) all but the moderately severe lispers displayed significantly slower lingual diadochokinetic rates. These findings suggest that clustering lispers into homogeneous severity subgroups before examining the relationships between their misarticulations and the lingual factors studied may offer important information regarding the diagnosis, treatment, and prognosis of their articulatory problems.