Lord Kelvin's temperature / heat flow experiments in 1846 (and onward) were duplicated by Apollo 15 astronauts on the lunar surface in June 1971. The holes were only 1.5 to 3.2 meters deep and the logging tool was stationary, but the results were recorded versus depth, so these surveys are the first petrophysical logs recorded off planet Earth.

Dave Scott of Apollo 15 running the first logs on the Moon in 1971

Apollo 17 astronauts repeated these temperature surveys and Apollo 16 and 17 crews also ran surface resistivity (EM style) surveys, similar to Conrad Schlumberger's early work in France back in the 1920's.

The lunar results: "The Moon is very dry". Golly, who would have guessed that? But don't despair. The moon has been mapped for neutron absorption and some areas absorb neutrons better than others. Hydrogen, hydrocarbon, or water? Or some other absorber (like iron for example)? Who knows.

Harrison "Jack" Schmidt deploying the Surface Electrical Properties equipment (SEP) during Apollo 17 mission, 1972.



Below are samples of the temperature logs taken during Apollo 15 in

1971,as well as sketches of some core samples.



First logs on the Moon, Apollo 15, 1971. These temperature versus depth logs parallel similar surveys by Lord Kelvin in 1869. The lunar temperature probes continued to transmit data to Earth after the astronauts left the Moon. On Terra, we were just beginning to record logs in digital form, and were a couple of years from sending digital logs by satellite to processing centers. X's represents projected stabilized temperature profile.

Apollo 17 density logs measured on core samples
(depths are in centimeters).

Apollo 17 temperature log, adjusted for diurnal variations, with derived thermal conductivity log.

Apollo astronauts brought back 2415 samples of rocks, soils, and cores weighing 840 pounds from the sis Lander sites on the near side of the moon. Only 32 pounds have been thoroughly analyzed and another 30 pounds are on display around the world. The balance sits in a vault in Houston. No one has explained why more anlysis has not been done.

Shallow cores were taken during Apollo 15, 16, and 17 missions. Rocks were also analyzed in-situ with X-Ray fluorescence and photography. Samples of rocks were returned to Earth and subjected to myriad tests, much as we have done for many years on Earth in the oil and mineral business. Sample lunar cores are illustrated below.

Sketches of cores taken by Apollo 17 crews on the Moon, 1972. Each core image is about 30 to 38 cm
 in length. Both driven and drilled cores were taken in the lunar soil.

The two drive-tube cores from Apollo 16 and 17 have never been seen by human eyes. They were sealed in their tubes under the vacuum of the moon and sealed in a second vacuum container at the vault in Houston. These pristine samples await investigation by "more sophisticated techniques" than are presently available. High resolution core photos like the one at the left  are at


For more information:

The Thermal and Electrical Conductivity Probe (TECP) on the Mars Phoenix Lander was designed to measure petrophysical properties on and near the surface of Mars. Physical properties of the near-surface of Mars were recorded during a 5 month period from June to October 2008.

Phoenix was equipped with a miniature back-hoe (called the Robotic Arm or RA for short) to dig trenches and deliver soil samples to other experiments inside the space craft. The TECP probe was mounted on the pivot at the RA scoop so it could be pressed into the surface soil or the wall of a trench.

TECP is the 4-pin device above the Robotic Arm scoop near
center of picture, the needles are 15 mm long  

The TECP is adapted from the commercial KD-2 multi-purpose probe made by Decagon Devices. The four-pin probe determines electrical conductivity by a two-pin LC (dielectric constant) approach and a redundant four-pin van der Pauw technique. The 4 pin EC method is similar to the Schlumberger four electrode AMNB surface resistivity electrode arrangement from the early 1900's.

Thermal conductivity is measured by a pulse-decay method using a heater and a thermocouple pair embedded in the pins.

Commercial version of the TECP device

The primary purpose of the TECP was to measure the concentration and nature of water in Martian soils in solid, “non-frozen,” liquid, and vapor states. Other objectives were to determine changes in the reservoirs of water when soil is freshly exposed and to characterize the movement of water in and out of the soil by measuring atmospheric humidity, temperature, and wind speed above the surface. Sounds a lot like reservoir evaluation and monitoring.

Photograph of the TECP instrument (top) and with the external cover removed to allow access to the
 electronics board (bottom). For each needle, the numerical designation and functionality are identified.

There are hundreds of ASCII data files available with the results of the TECP measurements, recorded versus time and day of acquisition. None appear to have been plotted versus depth in the trenches that were dug by the robotic arm. However there are lots of images that are strikingly similar to resistivity microscanner images.

True colour photo image of a Mars Phoenix trench. White areas are believed to be water ice, as
they appear to sublimate slowly after exposure to the Martian atmosphere. Samples were
processed in the Thermal Evolved Gas Analyzer (TEGA).

Phoenix was purposely placed on the Martian Arctic Plain. It is cold there, but not impossibly so - a mere 70 C colder than the Canadian Arctic Islands, where we have found more than 17 Tcf of natural gas. So who is ready to drill on Mars?

A log of minimum daily temperature for 120 Martian days (Sols) recorded by the Canadian built Phoenix MET station. (a Mars day is 24.65 Earth hours and a Mars year is 685.8 Earth days , so winter is nearly twice as loooooong as here at home).

The meteorological station on Phoenix was designed to monitor changes in water abundance, dust, temperature, and other variables in the Martian atmosphere. The Canadian Space Agency, York University, University of Alberta, Dalhousie University, Optech, and the Geological Survey of Canada designed and monitored the science operations of the station, which was built by Canadarm maker MacDonald Dettwiler and Associates Ltd. of Richmond, B.C.

For more information:

After Phoenix comes MARTE, a stratigraphic drilling program for Mars. Mars Astrobiology Research and Technology Experiment (MARTE) performed a field test simulating a robotic drilling mission on Mars in September 2005. The experiment took place in Minas de Riotinto in southwestern Spain, a highly relevant Mars analog site. The experiment utilized a 10 m class dry auger coring drill, a robotic core sample handling system, onboard science and life detection instruments, and a borehole inspection probe, all of which were mounted to a simulated lander platform.

Prototype robotic drilling rig for Mars

The prototype robot drilling/coring/logging machine reached 10 meters. Plans for 100 meter capability are in the works. The objective is to advance the search for life on Mars, but where there is life, there is a possibility of hydrocarbons. There is methane in the Martian atmosphere and spectroscopy mapping indicates the presence of clay and carbonate rocks, as well as the more obvious lava, dust, and other sediments. Interested parties can apply HERE for drilling concessions.

MARTE can drill, core, and run neutron and fluorescence logs. Neutron logs see water and ice; fluorescence logs see bacteria. The Ames tool is so sensitive, it can see a single bacterium. The core  samples can be analyzed on the drilling platform, then stacked for future examination. The remote sensing core analyzer can face or saw core samples, run spectrography, and prepare powder samples.

The borehole inspection system (BHIS) runs the neutron probe, a panoramic microscopic imager, and spectrometer. The borehole neutron log (BneuP) measures both thermal and epithermal neutron count rates. A surface version of the tool, to be carried on a Mars rover, is called (you guessed it) SneuP. It is intended as a dowsing machine, looking for hidden near surface water or ice deposits.

Sample of a BneuP log run in a manmade ice / soil test pit.

It's all real and working (almost). We just have to get it there and get to work.


As of Sep 2019, Voyager 1 is about 146.9 AU (21.986 bilion km) from Earth (add 0.52 billion km per year). It passed the termination shock in 2004, entering the heliosheath, reaching the heliopause in 2012, the boundary of the solar system and outer space. Its power supply is expected to fail sometime in 2025 so the longest log may be about 25 billion kms, after a trip of 48 years.


A log is a record of some observation versus time or distance, presented on an X-Y coordinate graph, a written narrative, or an audio or video report. Pilots, truckers. taxi-drivers, and tourists all keep logs. So do oil well drillers and other intrepid explorers who walk the Moon or operate robots on or near other planets. We even have logs from interstellar space. The Voyager 1 spacecraft, launched in Sept 1977, has recorded logs over the longest distances yet measured. 

The documented geological record of the Earth is the longest time-based record so far, unless you want to count the less-well documented history of the Universe beginning before the Big Bang.

Trajectories of Voyager and Pioneer spacecraft as they leave the solar system (2007). Voyager 1 is rising above the ecliptic and Voyager 2 is dropping below it. Who knows what these logging tools will find? Pioneer 10 and 11 are leaving more slowly and in opposite directions, but neither is still logging what they see.

All image credits: NASA/JPL

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