Month: September 2019

We’re familiar with the idea that Venus is a very hostile place: it has a thick, carbon-dioxide atmosphere mixed with other deadly gases that is so dense, it would instantly crush you were you to step onto the planet’s surface unprotected, and hot enough to boil you in the same moment as well as burn your skin away due to the presence of sulphuric acid. But for a long time, due to its enveloping clouds, it was believed that Venus could be a tropical paradise – a place of warm seas, lakes and rain forests, kept warm by the Sun whilst also protected from the worst of the heat by those thick clouds.

Now, according to a new study presented on September 20th, 2019 at the Joint Meeting of the European Planetary Science Congress (EPSC-DPS),that view of Venus as a warm, wet – and potentially habitable world. What’s more, but for a potentially massive cataclysmic event / chain of events, Venus might have remained that way through to modern times. The study comes from a team at the NASA Goddard Institute for Space Science (GISS), led by Michael Way and Anthony Del Genio.

The studies uses data gathered by two key NASA missions to Venus: the Pioneer Venus orbiter mission (1978-1992), and the Pioneer Venus Multiprobe mission (1978). The latter delivered four probes into the Venusian atmosphere, none of which were expected to survive impact with the planet’s surface, but instead sought to send their findings to Earth as they descended – although as it turned out, one did survive impact and continued to transmit data on surface conditions for more than an hour.

That data was coupled with a 3-D general solar circulation model that accounts for the increase in radiation as the Sun has warmed up over its lifetime and models used to define Earth’s early conditions, enabling the GISS time to develop five simulations to try to determine how surface Venus may have developed happened over time – and all five models produced very similar outcomes.

In essence, the models suggest that around 4 billion years ago, and following a period of rapid cooling after its formation, Venus likely had a primordial atmosphere rich in carbon dioxide, and with liquid water present on the surface. Over a period of around 2 billion years, much of the carbon dioxide settled in a similar manner seen on Earth, becoming subsurface carbonate looked in the planet’s crust. In the process, a nitrogen-rich atmosphere would have been left behind, again potentially not that different to Earth’s.

By about 715 million years ago – and allowing for the planet having a sufficient rotation period (16 Earth days or slower) – conditions would have reached a point where a stable temperature regime ranging between 20°C (68 °F) and 50°C (122 °F) could be maintained, with the models indicating that the planet could have oceans and / or seas and / or lakes varying in depth from about  10 m (30 ft) to a maximum of about 310 m (1000 ft), generating sufficient cloud coverage combined with the planet’s rotation to deflect enough sunlight and prevent the atmosphere from overheating. Further, had nothing further happened, these conditions could have more-or-less survived through to current times.

So what happened? That has yet to be fully determined, but the suggestion is that a series of connected global events came together in what might be regarded as a single cataclysmic re-surfacing of the planet. This is somewhat supported by data gathered by the Magellan probe (1988-1994). The GISS team suggest that this caused a massive outflow of the CO₂ previously trapped in the subsurface rock that in turn caused a runaway greenhouse effect that resulted in the hothouse we know today,  where the average surface temperature is 462°C (864°F).

Something happened on Venus where a huge amount of gas was released into the atmosphere and couldn’t be re-absorbed by the rocks. On Earth we have some examples of large-scale outgassing, for instance the creation of the Siberian Traps 500 million years ago which is linked to a mass extinction, but nothing on this scale. It completely transformed Venus.

– Michael Way – GISS Venus study joint lead

There are questions that still need to be answered before the models can be shown to be correct, which the GISS team acknowledge by stating further orbital study of Venus is needed. However, if the study’s findings can be shown to be reasonably correct, it could have relevance in the study of exoplanets.

Until now, it has been believed that planets with an atmosphere occupying a similar orbit around their host star would, like Venus, be subject to tremendous atmospheric heating, preventing liquid water or habitable conditions to exist on their surfaces. However, the GISS models now suggest that subject to certain boxes  being ticked, such planets occupying the so-called “Venus zone” around their parent stars could have liquid water present – and might actually be amenable to life.

Artemis and the Moon: Political Football

America is trying to return humans to the Moon by 2024 via a programme called Artemis. It’s an effort that requires funding, clear thinking, co-ordination and agreement. Right now, it would appear as if few of these are proving to be the case.

On the one hand, things do appear to be moving forward. According to a presentation on September 11th, the Lunar Orbital Gateway Platform (LOP-G) is on track. Both the Power and Propulsion Element (PPE -due for launch in 2022) and the Habitation and Logistics Outpost (HALO – due for launched in 2023), as the two core elements of the initial Gateway – remain on track. Even so, doubts have been sewn concerning its relevance, as I’ll come back to in a moment.

Elsewhere, the programme is far from smooth in its progress. On September 11th, the US House of Representative issued a draft  continuing resolution (CR) on the 2020 federal budget that provides no additional funding for NASA’s lunar ambitions – a result NASA Administrator Jim Bridenstine stated would be “devastating” to the development of the Artemis lunar lander.

Then at a hearing of the space subcommittee of the U.S. House of Representatives’ Science, Space and Technology Committee on September 18th, NASA’s acting associate administrator for human exploration and operations, Ken Bowersox (himself an ex-astronaut) came under heavy questioning on whether NASA really could achieve a successful human return to the Moon by 2024. His reply wasn’t entirely reassuring, “I wouldn’t bet my oldest child’s upcoming birthday present or anything like that.” He went on:

We’re going to do our best to make it. But, like I said, what’s important is that we launch when we’re ready, that we have a successful mission when it launches.

I’m not going to sit here and tell you that, just arbitrarily, we’re going to make. We have to have a lot of things come together to make it happen. We have to get our funding, we have to balance our resources with our requirements, and then we’ve got to execute it really well. And so, there’s a lot of risk to making the date, but we want to try to do it.

 – NASA acting associate administrator for human exploration, Ken Bowersox, September 18th, 2019

In particular, there are concerns surrounding NASA’s new Space Launch System rocket – vital to the effort. This is been plagued by issues to the point where Bridenstine suggested a critical test for the vehicle’s core stage and rocket engines, called the “green run” could be skipped in favour of “other means” of testing – an idea ultimately dropped after considerable push-back from within NASA and safety bodies. As it is, SLS will not be in a position to undertake all of the missions required to return humans to the surface of the Moon – such as delivering hardware to the halo orbit around the Moon that will be used by LOP-G, and so NASA has indicated it would be willing to use commercial vehicles such as the SpaceX Falcon Heavy for a number of cargo flights.

Continue reading “Space Sunday: Venus and getting to the Moon” →