Sample Analysis at Mars

Sample Analysis at Mars is a sophisticated analytical chemistry instrument suite onboard the Curiosity rover, which is the core component of the Mars Science Laboratory mission. Developed by a team led by the NASA Goddard Space Flight Center, it represents the most capable suite of instruments ever sent to another planet for chemical analysis. SAM's primary function is to perform detailed analyses of solid samples and atmospheric gases to assess the planet's past and present habitability.

Overview

The SAM suite is a cornerstone payload of the Curiosity rover, which landed in Gale crater in August 2012. It was designed and built by an international consortium led by principal investigator Paul Mahaffy at the Goddard Space Flight Center, with significant contributions from institutions like the Laboratoire Atmosphères, Milieux, Observations Spatiales in France and the Centro de Astrobiología in Spain. Weighing approximately 40 kilograms, it occupies more than half of the rover's science payload mass and is housed within the rover's front section. Its operation is intricately linked with the rover's Sample Acquisition, Processing, and Handling system, which drills into rocks and delivers powdered samples to SAM's inlet ports.

Scientific objectives

SAM's overarching goal is to conduct a detailed chemical and isotopic survey to understand the potential for Mars to have supported microbial life. A primary objective is to identify and quantify organic carbon compounds, which are the building blocks of life as known on Earth. The suite also aims to characterize the chemical and isotopic state of other light elements like hydrogen, nitrogen, and oxygen in both solid samples and the atmosphere. By analyzing the composition of the modern atmosphere of Mars, including trace gases like methane, SAM investigates current geological or potential biological processes. Furthermore, it seeks to understand the past environmental conditions within Gale crater by examining the mineralogy and chemistry of ancient sedimentary rocks.

Instrumentation

SAM integrates three primary analytical instruments into a single, complex package. A quadrupole mass spectrometer identifies and measures the masses of gases released from heated samples or directly from the atmosphere. A gas chromatograph separates complex mixtures of organic compounds before they enter the mass spectrometer, enhancing detection capabilities. A tunable laser spectrometer provides precise measurements of isotopic ratios in key atmospheric gases like carbon dioxide and methane, which are critical for understanding planetary evolution. The suite also includes a sophisticated sample manipulation system with 74 sealed cups, some containing chemical reagents for wet chemistry experiments to extract organics from minerals, and a pyrolysis oven that can heat samples to over 1000°C.

Operational history

Following the successful landing of the Curiosity rover in 2012, SAM underwent extensive checkouts and calibration before analyzing its first solid sample from the "Rocknest" aeolian bedform in late 2012. It has since analyzed dozens of drilled samples from sites like Yellowknife Bay, Pahrump Hills, and Vera Rubin Ridge. The instrument has also conducted numerous atmospheric analyses, monitoring seasonal changes and conducting enrichment experiments to detect trace gases. Operations have required careful planning by the science team at the Jet Propulsion Laboratory to manage the instrument's finite supply of consumables, such as the chemical derivatization reagents. Despite minor anomalies, SAM has functioned exceptionally well, far exceeding its primary mission duration.

Results and discoveries

SAM's findings have fundamentally advanced the understanding of Martian habitability. It detected simple chlorinated organic compounds in ancient mudstones at Yellowknife Bay, demonstrating that organic matter can be preserved in billion-year-old rocks. Measurements of isotopic ratios in the atmosphere have provided constraints on the historical loss of the Martian atmosphere to space. Crucially, SAM identified a repeating seasonal cycle of background methane levels in the atmosphere, with occasional significant spikes, pointing to active, though as yet unexplained, subsurface release mechanisms. The suite has also characterized the mineralogy of samples, identifying compounds like calcium sulfate and nitrates, and provided evidence for ancient freshwater lakes in Gale crater that offered chemically favorable conditions for life.

Category:Mars Science Laboratory Category:Space instruments Category:Mars spacecraft