One of my gripes with ‘The Martian’ movie was the depiction of the winds on Mars. The lower air density means that the sort of high speed winds we might experience on Earth carry far less of an impact on Mars. During its 72 flights in the Martian air, NASA’s ingenuity helicopter took meticulous records of the conditions. A new paper has been released and reports upon the wind speeds on the red planet at various altitudes. Previous models suggested wind speeds would not exceed 15 m/s but Ingeniuty saw speeds as high as 25 m/s.
Of all the planets in our Solar System, Mars is perhaps the most similar to Earth, similar but with stark differences. The weather on Mars is harsh and extreme, characterised by cold temperatures, a rarefied atmosphere and dust storms. The average temperature is around -60°C but it can reach a toasty 20°C in summer near the equator. It’s atmosphere is composed mostly of carbon dioxide and is about 100 times thinner than Earth’s so it offers little insulation or protection from solar radiation. On occasion, the winds on Mars whip up global dust storms that obscures the planet’s surface from view.
Our model of the Martian atmosphere was believed to be fairly accurate, that is until Ingenuity arrived and completed more than 70 successful flights. As part of the Mars 2020 mission and the first aerial vehicle to successfully complete powered flight on another world, Ingenuity revealed some surprising conditions. Surprisingly too perhaps, the first attempt at powered flight was supposed to be a technology demonstration but instead, it provided high resolution images to help direct the ground based rover and collected data from the atmosphere and became a key part of Mars 2020.
One of the outcomes from Ingenuity’s flights was a better understanding of Martian winds. In a paper written by Brian Jackson and team in the Planetary Society Journal, the team explained their rather ingenious approach. Knowing that the payload was severely limited on board, the decision was taken to use Ingenuity itself to confirm windspeeds. Previous studies had shown that the tilt of a stably hovering drone can be used to calculate speeds. Drones produce forward thrust by tilting in the direction they need to move, if they are stable and in a hover yet the wind is blowing, the drone will drift. Instead and to counteract the drift, the drone tilts flying into wind to maintain position relative to the ground, tilting more in a stronger headwind.
Measuring the tilt is relatively straightforward thanks to a collection of engineering sensors, cameras and accelerometers. With all of the information gathered by these onboard pieces of equipment and returned to Earth, the analysis and calculation of the drone at different altitudes has enabled the wind speeds to be accurately calculated.
The results were a surprise, showing that the winds on Mars were generally higher than anticipated. Speeds were measured at altitudes from 3 to 24 metres and were found to be blowing at anything up to 25 m/s. This perhaps is a result of Ingenuity’s unique capability of being able to measure speeds at different altitudes over a period of time. Previous measurements have been achieved from probes as they have descent through the atmosphere or from probes on the ground. Taking the success of Ingenuity forward, mission specialists working upon the Dragonfly rotorcraft that will be visiting Titan hope to be able to replicate the results and gain a better understanding of its wind profile too.
Source : Profiling Near-surface Winds on Mars Using Attitude Data from Mars 2020 Ingenuity
