EPSC-DPS 2019: Day 3

Editor’s note: We’re wrapping up a busy summer with one last conference: the EPSC-DPS joint meeting in Geneva, Switzerland. To celebrate the announcement of AAS Publishing’s new Planetary Science Journal, we’ll be bringing you some highlights from this planetary science conference all week!

Session: Leveraging Outreach in Planetary Defense

Communication about planetary defense efforts is a tricky game. Of course it’s important to share the information that scientists obtain about near-Earth asteroids and close approaches of small bodies from our solar system — but it’s also very easy for that information to take on a life of its own, leading to sensationalism and fear-mongering. We dropped in on this morning’s session on planetary defense outreach to learn more about its inherent challenges.

massive impact

Artist’s impression of a massive impactor (perhaps 1,500–2,000 miles across) that may have hit the Earth in its distant past. Note that the asteroids that we worry about for planetary defense today are much smaller than this. [NASA/Don Davis]

Patrick Michel (Observatoire de la Côte d’Azur, CNRS) pointed out an interesting problem: due to improvements in observational techniques, the number of newly detected near-Earth asteroids keeps increasing. As a result, reports of these objects enter into the news cycle more and more often — and to the public, this gives the appearance that the risk is inexplicably increasing.

To combat this effect, it’s important that scientists engage more effectively both with the media and with the public directly about planetary defense. According to Michel, the primary message should be that impact hazard is the least likely hazard, as compared to other natural disasters like tsunamis or earthquakes — and yet it’s also the only one that we have reasonable and feasible means to predict (by taking inventory of near-Earth objects) and mitigate (by developing and testing asteroid deflection tactics).

Conveniently, though interest in near-Earth asteroids is broad — for reasons of planetary defense, scientific study, resource mining, and more — all facets rely on gathering the same scientific information now. Understanding asteroid properties like composition, dynamics, response to impacts and stressors, etc., is a crucial first step, and communicating what we learn from this process will help to decrease misinformation about asteroid threats.

Speakers Regina Rudawska and Bernard Foing (ESA) and Phil Davis (NASA/JPL) described some of the ways that the U.S.’s and Europe’s major space agencies are working on planetary defense, and how this information is communicated.

ESA space safety posters

ESA’s space safety program spans a number of areas, as indicated by this beautiful set of posters (which you can download!). [ESA]

According to a recent study, Davis told us, roughly 6 out of 10 Americans view planetary defense as a top priority. The interest is there — but people have a lot of questions, and it would be better if answers came from us, rather than from “killer asteroid” misinformed news stories. Davis manages several major websites for NASA, so his web experience informs his perspective. “We know what questions people are asking; Google tells us! We just need to answer them, and to make sure our answers get out there [on the internet].”

Both NASA and ESA are working on this through website development and production and dissemination of engaging visuals (think NASA/JPL’s stunning space tourism posters or ESA’s lovely space safety program posters, also seen at right). Other institutes, like the Lunar and Planetary Science Institute, are working on engaging the public via interactive means, said Christine Shupla. She described games and activities that provided a broader and more positive view of asteroids, to counteract the bad rap these objects usually get.

Press Conference: Future Mission Updates

AIDA: DART and Hera

So, all that said, what are our major space agencies doing on the planetary defense front? Today’s press conference gave us an inside look at one major collaborative program: the Asteroid Impact and Deflection Assessment (AIDA) project. Patrick Michel (Observatoire de la Côte d’Azur, CNRS) opened by giving us an overview of the international program, which marks our first attempt to deliberately change the orbit of an asteroid (and learn as much as possible in the process!).

AIDA will target nearby asteroid Didymos, a binary asteroid (binaries account for ~15% of the asteroid population) made up of a primary body, Didymos A, that’s about 800 meters across and its moon, Didymos B, that is just 160 meters in diameter. Note that though Didymos is a near-Earth asteroid, it is not on a collision course with Earth; the goal of altering this asteroid’s orbit is purely for educational reasons, and not out of necessity!

The AIDA project consists of two major components:

  1. NASA’s Double Asteroid Redirection Test (DART) mission, which will aim a kinetic impactor at Didymos’s smaller, secondary asteroid, attempting to alter its orbit; and
  2. ESA’s follow-up Hera mission, which will arrive at the system a few years later and make detailed observations of Didymos, determining the consequences of DART’s impact.
DART and Didymos

The Didymos system and DART, with target Didymos B in the foreground. [NASA / JHUAPL]

While the most unique goal of the program is testing asteroid deflection tactics, there will be a number of other firsts! Didymos B will be the smallest asteroid we’ve ever studied, and this will also mark the first time we’ve used a radar to probe the subsurface structure of an asteroid.

Why was Didymos selected? Didymos B is roughly in the size range we worry about for planetary defense, so it’s a useful target to understand the response when a body of this size is struck. What’s more, the fact that this system is an eclipsing binary means that we can measure its orbital period very well using ground-based telescopes — and we’ll be able to use the same approach after DART’s impact to see exactly how the period changed.

So where does this mission stand? Nancy Chabot (Johns Hopkins Applied Physics Lab) reports that everything is on schedule for DART’s launch in July 2021, with impact occurring in September 2022.

DART schematic

Schematic shows the planned impact of DART on Didymos B, while observatories on Earth watch. [NASA/Johns Hopkins Applied Physics Lab]

The impact itself is a fascinating challenge. DART will be coming in at 6.6 km/s (that’s 14,800 mph!), and the Didymos system is a small target. In fact, DART won’t be able to distinguish between Didymos A and B until it’s within an hour of impact — yet it somehow needs to aim for the exact center of the tiny, 160-m moon! The DART team has addressed this challenge by equipping DART with a SMARTNav system — it will use its camera to autonomously distinguish between the two bodies, lock onto Didymos B, and aim itself at its center without any human intervention.

On its way in, DART will release a cubesat (a small satellite) with a camera that will observe the moment of impact. Important observations of the collision and the aftermath, however, will also come from ground-based telescopes on Earth — 11 million kilometers away.

So will this cause a spectacular deflection of the asteroid? Definitely not … watch the animation below for a rough idea of what we can expect. The goal is not to disrupt this asteroid or drastically alter its course, but rather to change its orbital period by a mere 10 minutes or so (that’s a ~1% change). Sounds minuscule, but that change of course is all that may be needed to deflect an asteroid past the Earth if we discover it while it’s still far enough away!

DART might seem like the main event of the AIDA project, but this mission will be greatly enhanced by follow-up observations after the dust has literally settled. Michael Küppers (European Space Astronomy Centre (ESA/ESAC) described plans for the Hera mission, the intended means of undertaking this follow-up.

Hera will be launched in 2024 and arrive at the Didymos system in early 2027. It will orbit around the system, taking images and doing detailed crater investigation as it spirals progressively closer. At the end of the mission, it will attempt to land either on the primary or the secondary asteroid (depending upon what we’ve learned about the bodies by that time).

Hera will carry two cubesats (small satellites) — the most advanced interplanetary cubesats yet. One of them will be responsible for conducting the first-ever radar subsurface exploration of an asteroid, which is sure to provide us with a wealth of information about this asteroid’s structure. All of the data Hera gathers will help us to better understand the system and how Didymos B responded to DART’s impact, further preparing us for the future possibility of undertaking a similar program in a case of planetary-defense necessity.

Venus vs. Earth

A size comparison of Venus and Earth. Though they are nearly the same size and density, the two planets evolved very differently. [NASA]


Why are the Earth and Venus so different? Venus, Earth, and Mars are basically a Goldilocks story: though they may have started out similarly, Mars ended up too cold for life, Venus too hot, and the Earth just right. Colin Wilson (University of Oxford) introduced the EnVision mission, a proposed orbiter mission to Venus that will study its structure and atmosphere, helping us to understand what shaped Venus into the hostile environment it is today.

Venus is a relatively unexplored planet — though dozens of Venus missions were launched in the 1970s and early 1980s (including 10 successful or semi-successful landers, none of which lasted more than 2 hours on Venus’s extreme surface), there have not been many missions to Venus since. EnVision would therefore provide important insight that we’ve been lacking.


Artist’s concept of the EnVision mission to Venus. [EnVision/VR2Planets/François Civet]

This orbiter would come equipped with instruments allowing it to image Venus at resolutions down to < 5m, measure magnetic fields, detect volcanic activity via thermal emission, measure subsurface structures down to 1 km in depth via radar, and map out Venus’s lithospheric/crust structure. It could also make detailed measurements of various species in Venus’s atmosphere.

EnVision’s goal is to address three main science themes:

  • Activity: How geologically active is Venus today?
  • History: How have Venus’s surface and interior evolved?
  • Climate: How did Venus’s atmosphere become so hostile?

The EnVision mission hasn’t yet been approved, but it’s a finalist in ESA’s M5 Space Science mission competition. If selected, it would launch in 2032 and conduct its science mission 2035–2038. Keep an eye out for more developments from this project in the future!

Mars Sample Return
Mars Sample Return mission

Diagram of the stages of the Mars Sample Return mission (click to enlarge). It’s quite simple, really. [ESA]

Like looking at long goals? Kelly Geelen (European Space Agency) rounded out the press conference with an overview of the proposed joint NASA/ESA Mars Sample Return mission, which would return the first sample from Mars to Earth in 2032.

This campaign has four distinct components:

  1. The Mars 2020 rover collects samples and caches them, leaving them on Mars’s surface for later retrieval. (NASA)
  2. A lander arrives on Mars’s surface in 2028 and collects the samples left behind, delivering them to an ascent rocket. The ascent rocket launches to a low Mars orbit in spring of 2029. (NASA)
  3. An Earth return orbiter then captures the canisters with the sample, returning to Earth in 2031. (ESA)
  4. The sample return canister, enclosed in an Earth re-entry module, arrives at Earth in spring 2032 and the sample is then received, curated, and investigated. (international)

This mission is still in the planning stages, and it’s clearly a huge cooperative effort. But Geelen hopes that in 10 years’ time we’ll have a sample getting ready to head back to us!