Heat Flow Programming Challenge

Using a microcontroller with compatible temperature sensors and output devices, students create a program that will detect temperature changes through a soil sample. They will then calculate the rate at which heat flows through the soil.

• Safety! This activity involves the use of heating elements. To avoid burns, ensure the safe use of these tools by expressing and modeling appropriate use. Keep incandescent bulbs from touching plastic tubs to avoid melting.
• Students can work in groups of two to four to develop code.
• If supplies permit, provide each group with a microcontroller, temperature sensor and output device. Otherwise, allow students to develop code and upload to shared microcontroller(s) for testing.
• If supplies permit, provide each group with a soil tub and heat source.

Vertical orientation (best with heat source below or above):

1. Partially fill one tub with soil.
2. Place the temperature sensor on top of the soil, centered, with connecting wires outside of the tub. (Protect the sensor in a sandwich or resealable plastic bag, if necessary.)
3. Measure the distance from the temperature sensor to the top or bottom of the soil (whichever will be nearest the heat source) and make note of the measurement for when students calculate the rate of heat flow.
4. Cover the sensor by adding more soil to the tub until it is level with the top.

Horizontal orientation (best with heat source to the side):

1. Partially fill one tub halfway with soil.
2. Place the temperature sensor on the soil, near the side of the tub that will be near the heat source, with connecting wires outside of the tub. (Protect the sensor in a sandwich or resealable plastic bag, if necessary.)
3. Measure the distance from the temperature sensor to the side of the tub that will be nearest the heat source and make note of it for when students calculate the rate of heat flow.
4. Fill the rest of the tub with soil.

Additional Tips

• Wrap tubs in aluminum foil or other insulating material to minimize heat entering from the sides of tub – but do not place it on side closest to the heat source.
• Tape connecting wire to the side of the tub so that repeated connecting and disconnecting from the microcontroller boards does not move the temperature sensors in the soil.
• The closer the sensors are to the side of the tub facing the heat source, the sooner the temperature changes will be evident. If the sensors are too far from the heat source, it might take a long time to detect temperature changes, but if the sensors are too close to the sides, there may not be enough of a difference in temperature to make meaningful distinctions.
• If using a single temperature sensor for every group in the entire class, there may come a point when the soil will not get any warmer, or the rate at which it changes by one degree becomes impractical for classroom application. Consider preparing multiple tubs that the sensor can be moved into, or move the sensor to the opposite end of the tub and rotate that end to be near the heat source.

NASA’s Mars InSight lander is equipped with three science investigations. One, the Heat Flow and Physical Properties Probe, or HP³, will use a self-hammering probe to burrow to a depth of up to 16 feet (5 meters) into the surface of Mars, deeper than any instruments have penetrated before on Mars. At this depth, measurements won’t be affected by changes in the seasons, all four of which InSight will experience during its Martian-year-long mission.

HP³ will pull a ribbon-like cable behind it. That ribbon is filled with temperature sensors that will measure heat escaping from the interior of the planet. These measurements will help scientists understand how much heat is inside the Red Planet and what’s generating that heat.

The probe will also generate its own heat pulse every 1.5 feet. The ribbon sensors will measure how these heat pulses change over time, giving scientists information about how quickly temperatures change with depth and how heat flows inside Mars.

• Which elements of the challenge proved to be more or less difficult than anticipated?
• What properties of the soil might be affecting the flow of heat?
• Were there differences in readings from group to group? If so, why?

• Have students develop code that will measure how long it takes for the temperature to change by 1 degree.
• Have students develop code to output the rate of change of the temperature to a display.
• Have students develop code to record data over time for later viewing, in addition to using the output device(s).

• Teachable Moment: NASA InSight Lander to Get First Look at ‘Heart’ of Mars
• Teachable Moment: NASA’s ‘Cyber Monday’ Mars Landing to Deliver Science Firsts
• InSight Lessons
• Mars Lessons
• Mars Activities for Students

• InSight Podcast: "On a Mission"
• "NASA/JPL Interns Join Mars Landing-Site Dude to Prepare for Touchdown" – Nov. 26, 2018
• "The 'Claw Game' on Mars Plays to Win" – Oct. 16, 2018
• "NASA's InSight Will Study Mars While Standing Still" – Oct. 24, 2018
• "The Mars InSight Landing Site is Just Plain Perfect" – Nov. 5, 2018

• InSight Mission Website
• Experience InSight Interactive
• NASA Mars Exploration Website