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

File 20180406 125187 1k9h41.jpg?ixlib=rb 1.1
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.

Read more:
Look up! Your guide to some of the best meteor showers for 2018

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:
Take it from me: I’m not signing up to become a space tourist just yet…

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.


Why New Zealand should not explore for more natural gas reserves

File 20180226 120776 1r3hubl.jpg?ixlib=rb 1.1
The New Zealand government is introducing legislation to become zero-carbon by 2050, but will consider new permits for coal mining, offshore oil drilling and fracking on a case-by-case basis.
from shutter, CC BY-ND

Ralph Sims, Massey University

New Zealand’s new coalition government has committed to introducing zero-carbon legislation that would set the country on a course to be carbon neutral by 2050.

At the same time, it is not ruling out new permits for coal mining, offshore oil drilling and fracking during a transition away from fossil fuels.

Natural gas is often touted as a “bridging fuel” to cut the use of coal for heat and power while moving towards a low-carbon economy. Also, this week’s report by the crown research institute Scion shows that New Zealand could build a renewable low-carbon transport fuels industry by switching to biofuels instead of natural gas. Developing new gas resources in New Zealand is a shortsighted strategy that could lead to stranded assets.

Read more:
2050 climate targets: nations are playing the long game in fighting global warming

Carbon budget

Carbon dioxide (CO₂) is a long-lived greenhouse gas. Each molecule released into the atmosphere from burning fossil fuels remains there for hundreds of years. Analysis by the Intergovernmental Panel on Climate Change shows that once we reach a total of 2,900 billion tonnes of carbon dioxide (Gt CO₂) in the atmosphere, the planet will likely exceed the internationally agreed target to keep warming below two degrees above pre-industrial levels.

More than 1,900 Gt CO₂ have already been emitted since the late 19th century. We are currently adding around 33 Gt CO₂ from fossil fuel combustion and 5 Gt CO₂ from deforestation every year. The atmospheric concentration of CO₂ has now surged to more than 403 parts per million, the highest in millions of years. The planet is already around one degree warmer than the average pre-industrial temperature.

This graphic shows that we have already used up around two-thirds of the total carbon budget to avoid exceeding a two-degree average temperature rise (with a 66% chance).
IPCC, Working Group 1, 2013, CC BY-ND

The remaining carbon budget, with a 66% chance of staying below the two-degree target, is now at about 800 Gt CO₂. At the current business-as-usual rate of fossil fuel combustion and deforestation, the total budget will be exceeded within 20 to 25 years.

Read more:
Fossil fuel emissions hit record high after unexpected growth: Global Carbon Budget 2017

By then, we will have used up around two-fifths of the known global reserves of coal, oil and natural gas. The remaining three-fifths will need to stay in the ground.

Gas as a transition fuel

Natural gas is described as a “transition fuel” that cuts the use of coal. This argument, and the case for providing greater energy security, is being used to justify exploration for deep sea oil and gas in New Zealand waters.

Displacing coal by burning conventional natural gas does indeed produce lower emissions, while providing the same heat or electricity services. A coal-fired power station produces around 900-1100 g CO₂/kWh generated; a gas-fired plant produces around 450-500 g CO₂/kWh. By way of comparison, a geothermal plant varies with the field but can emit up to 50 g CO₂/kWh and emissions from other renewable energy plants vary widely with the circumstances but tend to be much lower.

However, on a life-cycle basis, any carbon dioxide reduction benefits would be partially negated by leakage of methane (CH₄), the main component of natural gas. Leakage is inevitable during the extraction, distribution and use of natural gas. It is difficult to determine the level of leakage, but it is more certain that emissions from coal or gas plants are significantly higher than from a renewable energy plant of similar generation output.

Natural gas has the potential to extend the time before the carbon budget is used up, assuming it displaces coal that would then be left in the ground. But the use of gas cannot deliver the deep cuts in emissions that will be required to stay below two degrees.

Energy security and fossil fuel subsidies

Many nations, including New Zealand, aim to improve their energy security by shifting to more indigenous fossil fuel resources to reduce their dependence on imports and widely fluctuating prices. Exploring for more gas to meet local demands at contracted prices may make good political sense in the short term, but it exacerbates climate change.

Fossil fuel exploration, production and consumption is widely subsidised by many governments. The International Energy Agency estimated the value of consumer subsidies in 2016 was over US$260 billion.

Conversely, divestment away from fossil fuel companies is growing worldwide. For example, New York City is not only intending to divest US$5 billion of its holdings in fossil fuel assets, but also plans to sue the major oil companies over their contribution to climate change.

New Zealand’s economy without more gas

In New Zealand, natural gas is used to generate electricity and heat for industries, to produce methanol (mainly for export) and other petrochemical products such as urea. It also supplies around 277,000 domestic and commercial consumers in the North Island.

Currently around 1,200,000 tonnes per year (t/yr) of coal are consumed in New Zealand, mainly for heat and electricity, emitting around 2.6 Mt CO₂/yr. If all existing coal plants and heating systems were converted to gas, around 1.3 Mt CO₂/yr of emissions would be avoided. This would contribute a little towards the 20 Mt CO₂-eq/yr of emissions reductions needed to meet New Zealand’s current 2030 target under the Paris Agreement.

However, given the Government’s target to reach net-zero emissions by mid-century, gas will ultimately need to be entirely phased out together with coal and oil products. Therefore, the overall aims for New Zealand should be to:

  • use our existing reserves of natural gas wisely in order to gain maximum long-term economic benefits by maximising the return on investments already made, as well as reducing our annual CO₂ emissions by displacing coal and minimising methane leakage

  • invest significantly in research and development in sustainable energy, including low-carbon and economically viable alternatives for the current uses of existing gas supplies

  • clarify and quantify any fossil fuel producer and consumer subsidies and remove them in the near future

  • avoid the temptation to explore and develop new gas resources even if they appear to deliver short-term economic benefits; and

  • The Conversationinvest in renewable energy technologies, including biofuels, as long as they are produced from crop and forest residues and purpose-grown forests on marginal land, as identified in the Scion report.

Ralph Sims, Professor, School of Engineering and Advanced Technology, Massey University

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

Climate scientists explore hidden ocean beneath Antarctica’s largest ice shelf

File 20180124 107974 zcmtyp.jpg?ixlib=rb 1.1
The team used hot-water drilling gear to melt a hole through Antarctica’s Ross Ice Shelf to explore the ocean below.
Christina Hulbe, CC BY-ND

Craig Stevens and Christina Hulbe

Antarctica’s Ross Ice Shelf is the world’s largest floating slab of ice: it’s about the size of Spain, and nearly a kilometre thick.

The ocean beneath, roughly the volume of the North Sea, is one of the most important but least understood parts of the climate system.

We are part of the multi-disciplinary Aotearoa New Zealand Ross Ice Shelf programme team, and have melted a hole through hundreds of metres of ice to explore this ocean and the ice shelf’s vulnerability to climate change. Our measurements show that this hidden ocean is warming and freshening – but in ways we weren’t expecting.

Instruments travelling 360m down a bore hole, from the snow-covered surface of the Ross Ice Shelf through to the ocean below the ice. After splash-down at about 60m, they move through the bubble-rich upper ice and down into the dark bubble-free lower reaches of the ice – passing embedded sediment that left the coast line centuries ago.

Read more:
Antarctic glacier’s unstable past reveals danger of future melting

A hidden conveyor belt

All major ice shelves are found around the coast of Antarctica. These massive pieces of ice hold back the land-locked ice sheets that, if freed to melt into the ocean, would raise sea levels and change the face of our world.

An ice shelf is a massive lid of ice that forms when glaciers flow off the land and merge as they float out over the coastal ocean. Shelves lose ice by either breaking off icebergs or by melting from below. We can see big icebergs from satellites – it is the melting that is hidden.

Because the water flowing underneath the Ross Ice Shelf is cold (minus 1.9C), it is called a “cold cavity”. If it warms, the future of the shelf and the ice upstream could change dramatically. Yet this hidden ocean is excluded from all present models of future climate.

This satellite map shows the camp site on the Ross Ice Shelf, Antarctica.
Ross Ice Shelf Programme, CC BY-ND

There has only been one set of measurements of this ocean, made by an international team in the late 1970s. The team made repeated attempts, using several types of drills, over the course of five years. With this experience and newer, cleaner, technology, we were able to complete our work in a single season.

Our basic understanding is that seawater circulates through the cavity by flowing in at the sea bed as relatively warm, salty water. It eventually finds its way to the shore – except of course this is a shoreline under as much as 800 metres of ice. There it starts melting the shelf from beneath and flows across the shelf underside back towards the open ocean.

Peering through a hole in the ice

The New Zealand team – including hot water drillers, glaciologists, biologists, seismologists, oceanographers – worked from November through to January, supported by tracked vehicles and, when ever the notorious local weather permitted, Twin Otter aircraft.

As with all polar oceanography, getting to the ocean is often the most difficult part. In this case, we faced the complex task of melting a bore hole, only 25 centimetres in diameter, through hundreds of metres of ice.

A team of ice drillers from Victoria University of Wellington used hot water and a drilling system developed at Victoria to melt a hole through hundreds of metres of ice.
Craig Stevens, CC BY-ND

But once the instruments are lowered more than 300m down the bore hole, it becomes the easiest oceanography in the world. You don’t get seasick and there is little bio-fouling to corrupt measurements. There is, however, plenty of ice that can freeze up your instruments or freeze the hole shut.

A moving world

Our camp in the middle of the ice shelf served as a base for this science, but everything was moving. The ocean is slowly circulating, perhaps renewing every few years. The ice is moving too, at around 1.6 metres each day where we were camped. The whole plate of ice is shifting under its own weight, stretching inexorably toward the ocean fringe of the shelf where it breaks off as sometimes massive icebergs. The floating plate is also bobbing up and down with the daily tides.

The team at work, preparing a mooring.
Christina Hulbe, CC BY-ND

Things also move vertically through the shelf. As the layer stretches toward the front, it thins. But the shelf can also thicken as new snow piles up on top, or as ocean water freezes onto the bottom. Or it might thin where wind scours away surface snow or relatively warm ocean water melts it from below.

When you add it all up, every particle in the shelf is moving. Indeed, our camp was not so far (about 160km) from where Robert Falcon Scott and his two team members were entombed more than a century ago during their return from the South Pole. Their bodies are now making their way down through the ice and out to the coast.

What the future might hold

If the ocean beneath the ice warms, what does this mean for the Ross Ice Shelf, the massive ice sheet that it holds back, and future sea level? We took detailed temperature and salinity data to understand how the ocean circulates within the cavity. We can use this data to test and improve computer simulations and to assess if the underside of the ice is melting or actually refreezing and growing.

Our new data indicate an ocean warming compared to the measurements taken during the 1970s, especially deeper down. As well as this, the ocean has become less salty. Both are in keeping with what we know about the open oceans around Antarctica.

We also discovered that the underside of the ice was rather more complex than we thought. It was covered in ice crystals – something we see in sea ice near ice shelves. But there was not a massive layer of crystals as seen in the smaller, but very thick, Amery Ice Shelf.

Instead the underside of the ice held clear signatures of sediment, likely incorporated into the ice as the glaciers forming the shelf separated from the coast centuries earlier. The ice crystals must be temporary.

None of this is included in present models of the climate system. Neither the effect of the warm, saline water draining into the cavity, nor the very cold surface waters flowing out, the ice crystals affecting heat transfer to the ice, or the ocean mixing at the ice fronts.

The ConversationIt is not clear if these hidden waters play a significant role in how the world’s oceans work, but it is certain that they affect the ice shelf above. The longevity of ice shelves and their buttressing of Antarctica’s massive ice sheets is of paramount concern.

Craig Stevens, Associate Professor in Ocean Physics and Christina Hulbe, Professor and Dean of the School of Surveying (glaciology specialisation)

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