Remote Sensing Science and Engineering Background

Science Background

Planetary scientists try to answer big questions such as:

• How have the planets in our Solar System changed over time?
• Did life evolve only on Earth, or is there evidence that life evolved on other planets, too?

In these activities, youth will learn more about remote sensing tools and techniques that planetary scientists use to understand habitable environments on Mars, and how the planet has changed over geologic time.

If learners have previously completed the Engineering unit “Worlds Apart”, they learned about three types of remote sensing technologies: telescopes, filters, and LiDAR.

The science pathway supports exploration in the field of planetary science. Learners participate in a fictional NASA mission to choose a landing site for a Mars rover. They engage with and interpret Mars data captured during actual NASA missions. In these activities, they learn about the data obtained by remote sensing tools and techniques developed by engineers. They explore how planetary scientists use data from these technologies to understand habitable environments on Mars, and how the planet has changed over geologic time.

Why study Mars?

Mars may have once had a more Earth-like climate, but now it is a dry and cold desert. Scientists want to know how the climate on Mars changed and whether life could have evolved there. Mars is also closer to the Earth than many other planets, making it easier to send future missions there.

One reason to land on Mars is to collect samples that can be returned to Earth for detailed analysis in a laboratory. For example, volcanic rocks contain minerals that can be analyzed in a laboratory to find out how old the rock is, allowing scientists to get a much better understanding of how Mars changed over time. Some types of sedimentary rocks may contain organic (carbon-based) materials that give clues to whether life could ever have evolved on Mars.

Even without returning samples to earth, landing robotic rovers on Mars allows scientists to explore new areas and understand the processes that shaped the surface of the planet. Some of the most scientifically interesting locations to visit are places like impact crater walls or canyons where different rock layers are exposed in the walls. Layers of rocks are like the pages in a book that tell the story of the geologic history of an area.

But steep canyons and crater walls are dangerous places to try to land a spacecraft. There is a tradeoff between sites of interest to scientists, and sites that are safe to land on. The ideal site has a nice flat area to land on, and interesting minerals and landforms so that scientists can learn more about the planet’s past. In the following activities, youth will learn to use remote sensing to identify such a site.

What do scientists want to learn about Mars, and why is it necessary to land on the surface?

• What makes a good landing site?
• What NASA remote sensing data are available to help choose a landing site?

Today, Mars has low air pressure, only 1% as dense as Earth’s air pressure at sea level. Also, Mars is very cold, with temperatures typically around -67 °F (-55 °C). These conditions mean that Mars does not have liquid water on its surface today, though dry river valleys and dry lake beds indicate that liquid water once flowed across Mars’ surface billions of years ago.

Scientists are looking for evidence of habitable environments that existed in the past – places where liquid water existed on the surface for a long time. They are also interested in the age of rocks on Mars so that we can understand when the climate changed.

• How do we identify different landforms and how rough the surface is?
• How can we use maps of landforms (the shape of the land) to choose a landing site on Mars?

Volcanoes and impact craters dominate the topography of Mars. There are several very big volcanoes on Mars which are no longer active but have left behind large mountains and long lava flows. There are also places where rocks have been eroded in the distant past by flowing water, and places where the eroded sediments have accumulated and been compressed into sedimentary rocks. Mars also has some geologic processes that are going on today, which modify its landscape. For example, there are landslides, dust storms, and sand dunes that move around with the winds. Near the poles, water ice and carbon dioxide ice are deposited and removed with the seasons.

We can use topographic data to study the shapes of the land on the surface, called landforms, and get a good idea of the elevation at which different rock types are located, as well as where areas are flat and not too rough to land.

High-resolution images of the surface provide even more information, allowing scientists to identify landforms that are formed by water such as valleys, canyons, deltas, and alluvial fans. Images can also reveal whether the landscape is made of layered sedimentary rocks that might be formed by wind or water, or if volcanic rocks are more common.

• How can scientists find out whether life could have existed on Mars? How do we know how old Mars rocks are?
• How can we use infrared spectroscopy to identify a scientifically interesting landing site?

Identifying Minerals with Spectral Data

If learners have done the EE Worlds Apart Activities, they have already explored reflection of light with mirrors and filtering of light with cellophane. They used mirrors to explore the reflection of light in the Optical Obstacle Course, as a model for a space telescope. Then, they used cellophane as a model for a color filter, which filters out specific colors of the electromagnetic spectrum. For example, a blue color filter removes all colors from the visible spectrum except for blue.

In the science unit, learners explore ideas about types of light that we cannot see with our eyes because they are outside of the visible spectrum, such as infrared light. Here they will explore the reflection of specific colors of light using real NASA remote sensing data to identify specific minerals.

Remote sensing instruments called spectrometers allow us to “see” colors beyond the capabilities of our eyes. All materials (such as rocks, minerals, soils, plants, water, ice, and clouds) reflect and absorb different colors of light by different amounts. Just like color filters absorb some colors and let others pass through, different materials absorb or reflect different colors of light. Spectrometers measure the amount of reflected light at each wavelength. Line graphs of the reflected light vs. wavelength of the light are called spectra. Different minerals can be identified by their unique spectra, so spectroscopy can tell us a lot about the history of Mars.

Potential Landing Sites on Mars

To help youth work through the exercises presented here, it is helpful for educators to have some background knowledge about each of the locations that youth will be studying. All of the following locations are actual Mars rover landing sites or have been considered as landing site candidates.

Note: These descriptions are intended for educators, and include the “answers” for each of the sites. Learner-oriented descriptions of the sites are included in the adventure educator guide.

Gale Crater

The Mars Science Laboratory rover Curiosity landed in Gale crater in 2012 and continues to explore. Gale is a large impact crater. This site is interesting because the middle of the crater contains a mountain that is 3.4 miles (5.5 km) tall and is made of layered sedimentary rocks. The layered rocks have spectral signatures of clay minerals and sulfates, indicating multiple different environments involving water. The crater floor is also made of layers of sediment washed down from the crater rim. The floor is flat and safe for landing. Near the base of the mountain there are black sand dunes containing olivine and pyroxene.

In the HiRISE insets provided to the youth, location A shows layered rocks and a channel carved into the rocks by water and filled with sediment. Location B shows the black sand dunes.

Jezero Crater (Yez-er-oh or Jez-er-oh)

Jezero crater is one of the leading landing site candidates for the upcoming Mars 2020 rover. It is a large impact crater. It is interesting because the northwestern rim of the crater is breached by an ancient river channel which ends in a fan-shaped deposit of layered sedimentary rocks (possibly an ancient river delta). River deltas form when flowing water carrying sediment empties into a standing body of water like a lake. The Jezero delta contains clay minerals, and some of the crater floor deposits contain carbonate minerals. Much of the crater floor is covered by an old lava flow, which forms a flat surface with many small impact craters.

In the HiRISE insets provided to the youth, location A shows complex layers deposited in the delta. Location B shows the edge of the heavily cratered lava flow unit, with many small dunes at its base.

Nili Fossae Trough (Nee-lee Foss-eye)

Nili Fossae was considered as a landing site for the Curiosity rover and is also a candidate for the Mars 2020 rover. It is located in a large, long valley, called a graben, or trough. The floor of the valley contains a lava flow and some clay minerals. The eroding walls also expose clay minerals, possibly formed by circulating hot water. Olivine (a mineral that comes from volcanoes) is also exposed in the walls. The higher ground outside the valley is very rugged and resistant to erosion because of a lava flow.

In the HiRISE insets provided to the youth, location A shows some large sand dunes. Location B shows the edge of the cratered lava flow unit.

Iani Chaos (ee-Ah-nee Kay-oss)

This area is one of several “chaos” terrains on Mars, which are areas where a huge amount of underground water was released, resulting in giant floods and the collapse of the area where the water was stored. Within Iani Chaos, there are layered deposits of sulfate minerals. The location in the Student Data Packet was chosen as an example of a scientifically interesting location that would not make a good landing site because it is too rough and not safe to land there.

In the HiRISE insets provided to the youth, location A shows an outcrop of sulfate-bearing fractured rock. In the CTX data, layers can be seen in the rocks at this site, but at this higher resolution we can see that there aren’t obvious finer-scale layers. Location B shows the edge of a cratered lava flow unit, partially covered by small dunes.

Engineering Pathway

Remote sensing engineering is an interdisciplinary field that deals with the collection of data remotely, or from a distance. It has a wide variety of applications, from creating models of cities or natural landscapes to helping scientists predict the effects of climate change to precisely tracking orbiting satellites. Remote sensing engineers use techniques from many fields, such as cartography, optics, civil engineering, software engineering, and computer science.

In the activities of this pathway, youth are part of a team on a fictional NASA mission. They will engineer remote sensing devices to gather and visualize information about the surface of Mars. The data they collect will help the scientists meet their scientific goals, such as choosing a landing site that is best suited for gathering data on the geological features of the landscape and looking for evidence of water.

What Is Engineering?

What Is Technology?

Youth design technologies based on the problem they solve and imagine ways to improve the newer version.

How can we use the properties of light to design technologies that tell us about object we can not see?

Mirrors change the way light travels in order to see hidden objects.

Manipulating light and color can help interpret information from a distance that would otherwise be difficult to see.

Here are some definitions used in this unit: