美国宇航局蜻蜓与土星的超巨型卫星结合可能揭示导致生命的化学成分

新的[{” attribute=””>NASA mission to Saturn’s giant moon, Titan, is due to launch in 2027. When it arrives in the mid-2030s, it will begin a journey of discovery that could bring about a new understanding of the development of life in the universe. This mission, called Dragonfly, will carry an instrument called the Dragonfly Mass Spectrometer (DraMS), designed to help scientists hone in on the chemistry at work on Titan. It may also shed light on the kinds of chemical steps that occurred on Earth that ultimately led to the formation of life, called prebiotic chemistry.

Titan’s abundant complex carbon-rich chemistry, interior ocean, and past presence of liquid water on the surface make it an ideal destination to study prebiotic chemical processes and the potential habitability of an extraterrestrial environment.

DraMS will allow scientists back on Earth to remotely study the chemical makeup of the Titanian surface. “We want to know if the type of chemistry that could be important for early pre-biochemical systems on Earth is taking place on Titan,” explains Dr. Melissa Trainer of NASA’s Goddard Space Flight Center, Greenbelt, Maryland.

This illustration shows NASA’s Dragonfly rotorcraft-lander approaching a site on Saturn’s exotic moon, Titan. Credit: Johns Hopkins/APL

Trainer is a planetary scientist and astrobiologist who specializes in Titan and is one of the Dragonfly mission’s deputy principal investigators. She is also lead on the DraMS instrument, which will scan through measurements of samples from Titan’s surface material for evidence of prebiotic chemistry.

To accomplish this, the Dragonfly robotic rotorcraft will capitalize on Titan’s low gravity and dense atmosphere to fly between different points of interest on Titan’s surface, spread as far as several miles apart. This allows Dragonfly to relocate its entire suite of instruments to a new site when the previous one has been fully explored, and provides access to samples in environments with a variety of geologic histories.

At each site, samples less than a gram in size will be drilled out of the surface by the Drill for Acquisition of Complex Organics (DrACO) and brought inside the lander’s main body, to a place called the “attic” that houses the DraMS instrument. There, they will be irradiated by an onboard laser or vaporized in an oven to be measured by DraMS. A mass spectrometer is an instrument that analyzes the various chemical components of a sample by separating these components down into their base molecules and passing them through sensors for identification.

The colorful globe of Saturn’s largest moon, Titan, passes in front of the planet and its rings in this true color snapshot from NASA’s Cassini spacecraft. Credit: NASA/JPL-Caltech/Space Science Institute

“DraMS is designed to look at the organic molecules that may be present on Titan, at their composition and distribution in different surface environments,” says Trainer. Organic molecules contain carbon and are used by all known forms of life. They are of interest in understanding the formation of life because they can be created by living and non-living processes.

Mass spectrometers (see video below) determine what’s in a sample by ionizing the material (that is, bombarding it with energy so that the atoms therein become positively or negatively charged) and examining the chemical composition of the various compounds. This involves determining the relationship between the weight of the molecule and its charge, which serves as a signature for the compound.

如果你有一个来自另一个星球的样本，你会怎么做，你想知道它是否含有一种特定的分子……甚至可能是一种能揭示该行星可以维持生命的分子？ 面对这样的情况，科学家们使用了一种神奇的工具：质谱仪。 它完成了分离材料的艰苦工作，使科学家能够仔细观察样品并了解内部情况。 观看 NASA 戈达德太阳系探索部的这段视频，了解更多关于该仪器的信息。

DraMS 部分由 Goddard 的同一个团队开发，该团队开发了 火星样品分析 (SAM) 在好奇号火星车上。 DraMS 旨在扫描泰坦尼克号表面材料的样本 现场使用经过测试的技术[{” attribute=””>Mars with the SAM suite.

Trainer emphasized the benefits of this heritage. Dragonfly’s scientists did not want to “reinvent the wheel” when it came to searching for organic compounds on Titan, and instead built on established methods that have been applied on Mars and elsewhere. “This design has given us an instrument that’s very flexible, that can adapt to the different types of surface samples,” says Trainer.

DraMS and other science instruments on Dragonfly are being designed and built under the direction of the Johns Hopkins Applied Physics Laboratory in Laurel, Maryland, which manages the mission for NASA and is designing and building the rotorcraft-lander. The team includes key partners at Goddard, the French space agency (CNES, Paris, France), which is providing the Gas Chromatograph Module for DraMS that will provide an additional separation after leaving the oven, Lockheed Martin Space, Littleton, Colorado, NASA Ames Research Center at Moffett Federal Airfield in California’s Silicon Valley, NASA Langley Research Center, Hampton, Virginia, NASA Jet Propulsion Laboratory, Pasadena, California, Penn State University, State College, Pennsylvania, Malin Space Science Systems, San Diego, California, Honeybee Robotics, Brooklyn, New York, the German Aerospace Center (DLR), Cologne, Germany, and the Japan Aerospace Exploration Agency (JAXA), Tokyo, Japan.

Dragonfly is the fourth mission in NASA’s New Frontiers program. New Frontiers is managed by NASA’s Marshall Space Flight Center in Huntsville, Alabama, for the agency’s Science Mission Directorate Washington.