The Raman Spectrophotometer

Raman Spectrophotometers all have the same basic components:

  • A LASER source is needed to excite the target species.  Although the incident radiation can vary, a great deal of success was reported with a hollow cathode ion LASER that produces light at 224 and 248 nm.  Ultraviolet excitation has been particularly successful in obtaining spectra of organic molecules.  Mineral deposits such as carbonates respond well with these UV excitation wavelengths  as well as  325 nm.  (8, 9)
  • A filter collects the Raman scattered light (Stokes) and filters out the Raleigh and Anti Stokes light.
  • A diffraction grating bends the Raman shifted light according to wavelength.
  • A detector records the signal and passes the signal to a computer for decoding.  (10)

Clicking on this link will provide a "Virtual Raman" tour of a Raman Spectroscope.



Figure 10: Raman Spectroscopy Primer- An Introduction to JASCO Raman Spectrometers and the Raman technique,


To be able to withstand the rigors of interplanetary space travel and the harsh environment of the Martian surface, the instrument design must include the following:

  • The mass and volume must be reduced to a minimum due to the constraints of transportation.
  • Operation of the unit must be fully robotic.
  • There should be a minimum of moving parts that could possibly malfunction.
  • Energy requirements should be kept to a minimum.
  • The construction must be robust, able to withstand large temperature differences as well as other harsh surface conditions on the Martian surface. (11)

The unit diagrammed below is a proposed design for a future Martian mission.  In addition to the basic functioning components of all Raman Spectrometers, a small drill will be added to the sampling probe in order to analyze the soil just below the highly oxidizing surface of Mars.  For those units using SERS technology, a  metal platform will be added to promote sample analysis.

Figure 11:  

Proposed design for Mars Microbeam Raman Spectrometer (MMRS)


  Field testing of  a prototype Mars Exploration Rover (MER) has already been completed under desert conditions.  (Photo below.)  It is hopeful that this unit will be included in the missions planned during the next decade.


Photo 2: Mars Rover during desert testing


     Mars has consistently been the object of humankind's questioning nature for eons. From the ancients to modern day, Mars has held a place in our intellectual and cultural interests.  Click on "Why Mars?" to find some answers to this question.

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