Measuring the speed of winds on Mars using sound

• Mars has winds, despite its extremely thin atmosphere. How fast can Martian winds blow?
• Researchers can now measure wind speeds on Mars using a new method that involves the travel time of sound.
• The new method is faster than previous ones, works better measuring low-speed winds and can measure various kinds of winds.

Mars’ thin, windy atmosphere

Mars’ atmosphere is extremely thin, but it does have winds. The thinness of the atmosphere, however, makes measuring wind speeds difficult. Landers and rovers have been able to determine wind speeds with pretty good accuracy. But those measurements can still be improved. On August 13, 2024, researchers from the U.S. and Canada said they have a new method of measuring wind speeds on Mars, by using the travel time of sound.

The researchers published their peer-reviewed findings in The Journal of the Acoustical Society of America on August 13, 2024.

A new way to measure winds on Mars

Until now, landers and rovers on Mars have used various methods to measure winds. These include gauging the cooling rate of heated materials when winds blow over them and using cameras to image “tell-tales” that blow in the wind, akin to those used in sailing. Those techniques work, but scientists want to be able to measure wind speeds even more accurately.

Now, a team of researchers in the U.S. and Canada, led by Robert White at Tufts University in Medford, Massachusetts, have come up with a new method. Basically, it is a sonic anemometric (anemometer) system. An anemometer measures wind speed and direction. The system features a pair of narrowband piezoelectric transducers, which converts electrical charges into energy.

Using travel time of sound to measure wind speeds

The new system can measure the travel time of sound pulses through Martian air. White explained:

By measuring sound travel time differences both forward and backward, we can accurately measure wind in three dimensions. The two major advantages of this method are that it’s fast and it works well at low speeds.

The team tested the ultrasonic transducers and sensors over a wide range of temperatures and a narrow range of pressures in carbon dioxide. Mars’ atmosphere is composed of about 95% carbon dioxide. The tests showed only nominal error rates.

Replicating Martian conditions as closely as possible was crucial for the testing. The paper stated:

The acoustic conditions on Mars are similar to those in Earth’s stratosphere at 30 to 42 kilometers (19 to 26 miles) of altitude. Hence, testing was also conducted in dry air over the same range of pressures and temperatures with relevance to a secondary application of the instrument as a stratospheric anemometer for high altitude balloon missions on Earth.

Multiple wind speeds and various kinds of winds on Mars

The new technique also takes into account variables such as transducer diffraction effects and wind direction. The researchers said they should be able to measure multiple wind speeds at once – up to 100 measurements per second – as slow as 1 centimeter per second. Previously, other methods could only measure one wind speed per second. They could also only ideally measure speeds above 1 cm/s.

As White explained, the improved method will allow planetary scientists to measure different kinds of winds on Mars as well. Such measurements would also be crucial for future human missions to the red planet. Mars is famous for its dust storms and dust devils, which could endanger habitats. White said:

By measuring quickly and accurately, we hope to be able to measure not only mean winds, but also turbulence and fluctuating winds. This is important for understanding atmospheric variables that could be problematic for small vehicles such as the Ingenuity helicopter that flew on Mars recently.

The system we’re developing will be 10 times faster and 10 times more accurate than anything previously used. We hope it will produce more valuable data as future missions to Mars are considered and provide useful information on the Martian climate, perhaps also with implications for better understanding the climate of our own planet.

Bottom line: Scientists have developed a new technique – using the travel time of sound – to measure the speeds of winds on Mars with greater accuracy than ever before.

Source: Modeling and characterization of gas coupled ultrasonic transducers at low pressures and temperatures and implications for sonic anemometry on Mars

Via American Institute of Physics (EurekAlert!)

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