Launching in May, the InSight mission will measure marsquakes to explore the interior of Mars

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InSight aims to figure out just how tectonically active Mars is, and how often meteorites impact it.

Katarina Miljkovic, Curtin University

When we look up at Mars in the night sky we see a red planet – largely due to its rusty surface. But what’s on the inside?

Launching in May, the next NASA space mission will study the interior of Mars.

The InSight (Interior exploration using Seismic Investigations, Geodesy and Heat Transport) spacecraft will be a stationary lander mission that measures seismic activity on Mars (often referred to as marsquakes) as well as interior heat flow.

Read more:
A brief history of Martian exploration – as the InSight Lander prepares to launch

By listening to and probing the Martian crust and interior, the project aims to understand the formation and evolution of Mars.

The InSight mission is scheduled to launch from California in early May, with landing on Mars planned for November. The expected lifetime of the mission is at least two years.

Origins of marsquakes

The payload on board InSight includes the seismic instrument SEIS (Seismic Experiment for Interior Structure). Its task is to record seismic activity, or vibrations, of the planet.

Apart from shaking the ground while passing, seismic waves can be extremely useful in telling us about the structure of planetary interiors. Seismic waves travel at different speeds when passing through different materials. Processing their arrival time and strength via recorded seismographs is a clever way to learn about the interior structure of a planetary body – such as the crust, the next layer down (the mantle), and the core.

Seismic activity on Mars could be caused by a number of processes. For example, shallow marsquakes could originate from meteoroid strikes, and deep marsquakes could come from martian tectonic activity (the movement of tectonic plates at the surface of the planet).

It is generally believed that tectonic processes could have shaped Mars in its early evolution, similar to the Earth. However, unlike the Earth in younger ages, Mars has become largely tectonically dormant.

We think lots of meteoroids hit Mars

Considering that tectonics on Mars may not be reminiscent of what we see on our planet, we suspect that meteoroid strikes will play a major role in causing marsquakes.

On Earth, frequent and small meteoroids most often burn up in the atmosphere and appear to us as a form of “shooting star”. When a rock from space moving at supersonic speed encounters the terrestrial atmosphere, the air in front of it gets compressed extremely quickly. Temperature rises and heat builds up, so the rock starts to shine bright under the process of its destruction.

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However, on Mars we think that meteoroids may not necessarily burn up entirely upon encountering the martian atmosphere. This is simply because Mars has a less dense atmosphere than the Earth – so incoming meteoroids have a higher penetrating power. These impact events would produce seismic disturbance in the atmosphere, and also likely in the ground.

Detecting meteoroid strikes on planetary bodies began with the lunar Apollo program. Apollo missions carried seismometers to the Moon, and as a result we had a network of seismometers that operated on the Moon from 1969-77.

During its lifetime, the Apollo seismic network recorded shallow quakes produced by frequent meteoroid bombardment. Considering that the Moon does not have an atmosphere to protect its surface from the incoming meteoroids, the Apollo seismic network provided heaps of seismic data from the Moon. These impact-induced seismic moonquakes provided the first constraints about the thickness of the lunar crust as well as structure of crust and deep interior.

We’ve tried to measure Mars seismic activity before

During the lunar exploratory boom with the Apollo program, NASA also launched Vikings 1 and 2 to Mars in 1975. These became the first missions to land on Mars, and each Viking mission carried a seismometer.

While instruments on Viking have collected more data than expected, the seismometer on Viking Lander 1 did not work after landing. The seismometer on Viking Lander 2 demonstrated poor detection rates, with no quakes coming off the ground (as it had remained on the Lander).

To date, we have had no other seismic station on any extraterrestrial planetary body. This makes InSight the first-of-its-kind mission to be placed on Mars. While its design relies on proven technologies from past missions, it is ground-breaking in terms of expected science goals.

Instead of making orbital remote sensing surveys or roving on the surface similar to other rovers, InSight has a different goal to previous Martian missions.

Read more:
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Why are we so interested in the subsurface of Mars?

Mars and Earth differ in size, temperature, and atmospheric composition. But similar geological features such as craters, volcanoes, or canyons can be observed on both planets. This implies that the interior of Mars may be similar to Earth’s.

It is also quite likely that there was liquid water on the surface of ancient Mars, which was the time Mars could have been very similar to Earth. So Mars could answer questions about the ancient habitability of our solar system.

Unlike potentially habitable planets orbiting distant stars, Mars is reachable within our lifetime. Discovering martian crustal properties is of great importance when it comes to planning landing missions and investigating signs of extraterrestrial habitability.

The ConversationMy role in the InSight mission is to work with the science team in analysing the data (impact-induced seismograms and any respective orbital imagery) to work out what kind of impacts had occurred during the mission lifetime.

Katarina Miljkovic, ARC DECRA fellow, Curtin University

This article was originally published on The Conversation. Read the original article.


Mission over: the final countdown to Cassini’s fatal plunge into Saturn

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An illustration of Cassini as it plunges into Saturn’s atmosphere.

Ed Kruzins, CSIRO and Richard Stephenson, CSIRO

When the Cassini space probe makes its final descent into Saturn later today, data from the final nine hours of the mission will be sent back to NASA’s tracking station in Canberra, Australia.

As the probe descends, it will capture images and data from Saturn and its atmosphere, revealing more of the planet’s secrets. Under the spacecraft’s normal operations, its instruments first store and later forward images and data to Earth.

But in Cassini’s final hours, it will be transmitting home in real time, with the signals picked up by the CSIRO-managed Canberra Deep Space Communication Complex (CDSCC).

Read more: The secrets of Titan: Cassini searched for the building blocks of life on Saturn’s largest moon

The CDSCC is part of NASA’s Deep Space Network, one of three tracking stations around the world that provide vital two-way radio contact with Cassini and 30 other spacecraft including Voyagers 1 and 2.

Cassni’s final journey in local AEST times.

Cassini’s final bonanza of data, transmitted as weak radio signals, will take 83 minutes to travel 1.5 billion km at the speed of light to reach the giant dish antennas in Canberra.

At an estimated 9:54pm AEST tonight (September 15), CSIRO’s team at CDSCC will capture the final signals as Cassini, travelling at more than 111,000km per hour, plunges into Saturn’s atmosphere.

How to destroy the probe

NASA decided to safely dispose of Cassini into Saturn, ending its mission as a shooting star. With the spacecraft nearly out of fuel and possible loss of control, this plan will prevent accidental collisions with any of Saturn’s moons and potential biological contamination by microbial stowaways from Earth.

Viewed from Saturn, the last moments of Cassini would look similar to a meteor entering Earth’s atmosphere.

An illustration of Cassini breaking apart after entering Saturn’s atmosphere.

From Earth, the world will await the bittersweet moment when NASA’s Jet Propulsion Laboratory mission control announces loss of signal. Cassini’s final call home will have been made.

It will mark the end of a 20-year mission, a joint venture between NASA, the European Space Agency and the Italian Space Agency.

Mission objectives

Inspired by the earlier flypast by the twin Voyager spacecraft, the two-part mission was actually known as the Cassini-Huygens mission.

The main craft was designed to study Saturn and its environs, while the piggybacking Huygens probe was to land on Titan, the planet’s largest moon.

Throughout its odyssey, every step of Cassini’s journey has been followed by the dishes at CDSCC in Canberra. It was the first tracking station to make contact with Cassini after its launch from Cape Canaveral in October 1997.

The Cassini spacecraft and Huygens probe begin their seven-year journey to Saturn after a successful launch on October 15, 1997.

It then tracked Cassini throughout its seven-year journey to Saturn, handling the vital communications as it arrived and was placed into orbit around the planet in July 2004.

As the first spacecraft to orbit Saturn, it has studied the planet, its rings and its 62 moons, seven of which were discovered by Cassini.

In 2005 the Huygens probe transmitted data as it landed safely on the surface of Titan. This was the first landing on a world in the outer Solar System.

The Huygens probe’s descent to Titan.

Saturn’s wonders revealed

Cassini has now witnessed almost half a Saturn year, which is 29 Earth years long.

While Voyagers 1 and 2 had spectacular encounters with the outer planets interspersed by years of travel, Cassini has delivered science on a daily basis.

Like a Swiss Army Knife of spacecraft, Cassini has a plethora of scientific instruments on board.

Eight of Cassini’s science instruments are planned to be turned on during the final plunge, including the Ion and neutral Mass Spectrometer (INMS).

While the most inspiring data is the images, for staff at CDSCC the excitement has centred around performing dozens of unique radio science experiments with the Cassini team.

Using a process called bistatic radar, which is the deep space version of sonar, the data received made it possible to measure the size and distribution of particles in Saturn’s rings.

Saturn reigns supreme, encircled by its retinue of rings. You can also see Saturn’s famous north polar vortex and hexagon.
NASA/JPL-Caltech/Space Science Institute

It was also used to map the terrain and depths of ethane and methane lakes on the surface of Titan. For Cassini’s final bistatic observations of Titan earlier this year, key members of Cassini’s science team travelled to Canberra to witness the data coming into CDSCC first-hand.

Staff found it exhilarating to watch the pure excitement on the faces of Cassini’s team standing in their Canberra control room as the spacecraft’s faint signals were being received.

Bistatic scattering reveals the details on Titan.

To some of us, the data may have appeared as not much more than a slightly higher peak in a hash of radio noise, but to the mission team it meant discovering a shoreline or a lake bottom on the surface of a world more than a billion kilometres away. Being a part of these discoveries was a proud moment for CDSCC and its CSIRO team.

The rest of the probes

As we say goodbye to Cassini, CDSCC continues to track more than 30 other spacecraft, not only NASA probes but also those of other international space agencies in Europe, Japan and India.

The Canberra antennas still support both Voyager spacecraft for several hours each day, receiving data from the edge of the Solar System and beyond.

Canberra Deep Space Communication Complex will keep track of other spacecraft after Cassini’s final plunge into Saturn.

NASA’s Juno has only just begun its primary mission, transmitting scientific data as it orbits Jupiter. Its highly elliptical orbit brings the spacecraft dangerously close to Jupiter (5,000km) before retreating away from the radiation-intense planet.

New Horizons, which flew past Pluto in 2015, has set a course for an encounter with a Kuiper Belt object on January 1, 2019. The spacecraft is periodically woken from hibernation to check system functions before being returned to slumber.

The next few years will see a quantum shift as the Deep Space Network moves to supporting proposed human missions to the Moon, asteroids and Mars.

Some key numbers for Cassini’s Grand Finale and final plunge into Saturn.

For now though, CDSCC is concentrating on Cassini’s final moments, delivering its last breath of data to NASA scientists who will continue to study the information for decades to come.

Read more: A look back at Cassini’s incredible mission to Saturn before its final plunge into the planet

Using the big 70-metre antenna dish at CDSCC as the prime receiver, it will be backed up by a smaller 34m dish. To add even further redundancy into the system, the European Space Agency has a 35m dish in New Norcia, Western Australia, which will also listen to Cassini’s radio whispers.

Cassini’s final hours will be a bittersweet moment for the CDSCC team, losing a spacecraft that for 20 years had become a daily part of our lives.

We will say a fond farewell to an incredible mission, safe in the knowledge that we’ve been a part of an adventure that revealed Saturn as a real place, full of wonders, for future generations to explore.

There are a several ways to watch Cassini’s final hours, including:

You can also follow Cassini on Twitter @CassiniSaturn and Facebook at NASACassini.

The Conversation


Ed Kruzins, Facilities Program Director Nasa Operations Canberra Deep Space Communication Complex , CSIRO and Richard Stephenson, Deep Space Network Operations Supervisor, CSIRO

This article was originally published on The Conversation. Read the original article.

Montserrat: Return of the Mountain Chicken Frog

The link below is to an article reporting on what is hoped will be the beginning of the return of Montserrat’s Mountain Chicken Frog after a mission to save the frog from a deadly fungal disease.

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