Killer Asteroids – Are they??
Protecting Humanity!
A hosted article by
Ilavenil T
“Extinction
is the rule. Survival is the exception” - Carl Sagan
Biennial
exercises by NASA simulate asteroid impacts to prepare international
response strategies. Scenarios like
these use
real data to test emergency preparedness and explore deflection techniques like
the DART mission.
Ilavenil T
This
is Ilavenil’s second article as a guest blogger under my banner. The first one appeared
in February this year and can be accessed here.
On
the theme of potentially dangerous near-earth objects, the present article is
both complementary and supplementary to my own in September 2023 (see here),
which had been inspired by her involvement in asteroid hunting as a Regional
Training Volunteer in the International Astronomical Search Collaboration
(IASC).
[This article appears as
an interlude to the present series of articles on Pioneers of Quantum
Theoretical Physics commemorating the International Year of Quantum Science and
Technology, IYQ25.]
The portents
We all saw headlines and
videos like these in January and February 2025:
Astronomers
spot asteroid that may be heading for the earth. The Hindu (Feb 5,
2025)
UN monitors asteroid with a tiny
chance of hitting Earth. BBC
(Feb 3, 2025)
Revised Calculations Just Increased
Asteroid 2024 YR4's Chances of Hitting Earth (Odds: 1-in-43) (TerritorySpace Youtube Channel,
February 8, 2025)
Not only was the media talking
about an impending impact on Earth, a map was also published showing the
probable areas where it could happen, including a line right across India (see
map below). This was just scare mongering.
Here are some valid
questions about these scary portents:
·
Why do the media report possible asteroid impacts so often?
·
An asteroid will never hit the Earth, right?
·
What is being done about it?
In this article I’ll
attempt to answer these questions.
Why do they report
possible asteroid impacts so often?
The announcements keep
coming because there are literally hundreds of NEOs (Near-Earth Objects) that
cross the Earth’s orbit every year. NEOs are asteroids and comets that orbit
the Sun with a perihelion distance* less than 1.3 au@. According
to the Centre for Near Earth Object Studies (CNEOS), there are 17 objects that
will come within a distance of 5 lunar distances within the next year (between
April 26, 2025 and April 26, 2026). One of them will come even closer than the
Moon.
[*Perihelion distance: The
closest distance between an object and the Sun.
@ au: Astronomical Unit –
the average distance between the Earth and the Sun - 149,597,870 km]
Here are the orbits of the
five NEOs that will come the closest within the next year, generated through
the CNEOS orbit viewer.
The following table* shows
close approaches to the Earth by near-Earth objects (NEOs)
|
Object |
Close-Approach (CA)
Date |
CA Distance |
CA Distance |
|
2025 HW1 |
2025-Apr-28
17:41 ± 00:06 |
3.160 |
3.137 |
|
2025 FA22 |
2025-Sep-18
07:04 ± 03:33 |
2.162 |
2.022 |
|
2025 DQ |
2026-Feb-21
17:53 ± 00:08 |
3.018 |
2.957 |
|
2025 BL |
2026-Jan-17
07:14 ± 01:31 |
4.663 |
4.171 |
|
2024 TB7 |
2026-Apr-07
14:21 ± 07:17 |
4.848 |
2.330 |
|
2023 PX |
2025-Aug-22
11:21 ± 1_10:07 |
2.416 |
2.413 |
|
2023 DZ2 |
2026-Apr-04
02:01 ± 00:02 |
2.633 |
2.633 |
|
2023 CM2 |
2026-Feb-21
12:56 ± 8_10:52 |
4.164 |
1.999 |
|
2022 SS2 |
2025-Sep-13
15:22 ± 3_03:06 |
2.369 |
1.847 |
|
2022 OB5 |
2026-Jan-14
07:21 ± < 00:01 |
1.679 |
1.679 |
|
2022 OC3 |
2026-Jan-31
23:41 ± 01:49 |
1.301 |
1.288 |
|
2021 PJ1 |
2025-Aug-15
04:38 ± 01:52 |
4.357 |
4.074 |
|
2015 XX168 |
2025-Dec-18
20:34 ± 07:53 |
4.693 |
1.670 |
|
2015 VO142 |
2026-Mar-17
05:12 ± 07:10 |
2.715 |
2.396 |
|
2013 GM3 |
2026-Apr-14
16:15 ± 07:56 |
0.678 |
0.020 |
|
2010 RA91 |
2026-Mar-22
01:13 ± 00:01 |
4.671 |
4.669 |
|
2007 EG |
2026-Mar-15
02:24 ± < 00:01 |
4.457 |
4.457 |
CA Distance Nominal: The most likely closest-approach distance (centre
of the Earth to centre of the NEO)
CA Distance Minimum: The minimum possible close-approach distance
(centre of the Earth to centre of the NEO)
LD: Lunar Distance - the mean semi-major axis length of the orbit of
the Moon around the Earth - 384400 km. 384400 km.
*From: https://cneos.jpl.nasa.gov/ca/
Even though the numbers
are large, the distances are also large. For example, the mean minimum closest
approach distance of the objects in the table is 9,89,549 km. That is almost
four times the distance between the Earth and the Moon. As for the object that
will come closer than the Moon, it is only between 15 - 33m in size. It will
burn up even if it touches the Earth’s atmosphere.
In addition to this, bolides
and fireballs (unusually bright meteors) are tracked regularly. These
also number in the hundreds, as seen in the map below.
Though the map may look
frightening, it is important to remember that these are fragments of comets and
asteroids which burnt up in the atmosphere without actually impacting the
Earth. These numbers show why there are so many announcements of asteroids
coming close to the Earth.
An asteroid will never hit
the Earth, right?
The answer to this
question might be disheartening. Asteroid impacts are regular occurrences, and
have occurred many times on the Earth in its past history.
Some of the largest impact
structures on the Earth are*:
|
# |
Crater Name |
Age (Years) |
Location |
Diameter (km) |
|
1 |
Vredefort Crater |
2,023,000,000 |
South Africa |
(170 – 300) |
|
2 |
Sudbury Basin |
1,849,000,000 |
Canada |
130 |
|
3 |
Acraman Crater |
~590,000,000 |
Australia |
Up to 90 |
|
4 |
Woodleigh Crater |
~364,000,000 |
Australia |
~120 |
|
5 |
Manicouagan Crater |
214,000,000 |
Canada |
100 |
|
6 |
Morokweng Crater |
146,000,000 |
South Africa |
75 - 150 |
|
7 |
Kara Crater |
70,300,000 |
Russia |
~120 before erosion |
|
8 |
Chicxulub Crater |
66,000,000 |
Mexico |
200 |
|
9 |
Popigai Crater |
35,700,000 |
Russia |
90 |
|
10 |
Chesapeake Bay Crater |
35,500,000 |
United States |
85 |
Information compiled from
Wikipedia
*There are other
structures similar to impact craters, some even larger, which are still under
investigation about the probable cause.
Looking at the table,
there seems to be a trend where the craters become smaller as we move from the
past to the present. That is not true – the actual reason is that the larger
the crater, the better it withstands the geologic processes of the Earth, such
as erosion and the rock cycle, where rocks are transformed from one type to
another.
The Vredefort crater in
South Africa was the result of the Earth being hit by an impactor that was
20-25 km in diameter. It did not cause a mass extinction since the Earth was
inhabited only by unicellular organisms at the time. However, the impactor that
caused the extinction of almost 75% of species was between 10-15 km in
diameter.
This is a satellite image
of the Vredefort impact structure, with the Vaai river running across it.
Here are the locations of
some of the largest impacts on earth:
The interactive form of
this map, with details on all the craters, is available at https://upload.wikimedia.org/wikipedia/commons/c/cc/Earth_Impact_Database_world_map.svg
It is highly probable that
we will be hit with a large impactor in the future.
What is being done about
this?
Protecting humanity from a
species-ending asteroid (or comet) strike is the main objective of Planetary
Defence. The term “Planetary defence” includes the detection, tracking, and avoidance
of potential asteroid impacts on Earth. It is led by NASA's Planetary
Defense Coordination Office (PDCO).
Detection and Tracking
The detection and tracking
of Near-Earth Objects, including asteroids and comets, is important not only
for planetary defence but also to accurately map the solar system and improve
our understanding of gravitational perturbations. (Gravitational perturbations
are small changes in a celestial body’s orbit when another body passes near it,
and they happen because of the gravitational force between the objects).
NASA's NEOWISE (Near-Earth
Object Wide-field Infrared Survey Explorer) mission repurposed the
Wide-field Infrared Survey Explorer (A NASA infrared space telescope) to detect
and characterize asteroids and comets using infrared observations. It was
decommissioned in August 2024.
The Catalina Sky Survey is conducted at the
Steward Observatory's Catalina Station, located near Tucson, Arizona, in the
United States. The Catalina Sky Survey (CSS) uses three telescopes, all located
in the Catalina mountains - a 1.5 meter telescope and a 1m telescope on Mount
Lemmon and a 68 cm telescope on Mount Bigelow. The telescopes search
for NEOs, and operate on every clear night except a few around the full moon.
As of 2020, the Catalina Sky Survey is responsible for almost 47% of new
Near-Earth Object Discoveries.
The Panoramic Survey
Telescope and Rapid Response System (Pan-STARRS)
The Pan-STARRS system
consists of two 1.8m telescopes located at Haleakala in Hawaii. They
stand out in having very large fields of view and are equipped with digital
cameras with short exposure. This adds up to a lot of observation and a lot of
data to be analysed, which is why the system also includes a computing
facility. In addition to surveying the sky for moving or variable objects, the Pan-STARRS
system also produces accurate astrometry and photometry of existing objects.
A data release by Pan-STARRS
in January 2019 was the largest volume of astronomical data ever released, at
1.6 petabytes.
Role of Citizen Scientists
and the IASC in Spotting Asteroids
Citizen scientists play a
vital role in asteroid detection through initiatives like the International
Astronomical Search Collaboration (IASC). This program provides
high-quality astronomical data to volunteers worldwide, enabling them to
participate in asteroid discovery campaigns.
The citizen scientists,
mainly school students and some interested adults, use a customized version of Astrometrica
- a software meant to precisely measure
the positions and movements of celestial bodies - to analyse images and
identify moving objects that may be asteroids. Their contributions have led to
the discovery of thousands of asteroids, including near-Earth objects.
IASC has facilitated the
discovery of approximately 12,000 main-belt asteroids and several near-Earth
objects over the past 15 years, involving over 50,000 citizen scientists from
96 countries.
I have worked with
hundreds of students and eager adults as a Regional Training Volunteer in IASC.
Here is a map of the provisional discoveries made by the people I have guided,
as on October 16, 2024.
Image compiled using the Small body database
For more information on my
work in this field and the procedure by which students detect asteroids, please
check this: Asteroid Hunt
Databases
The discoveries are
collated in the following databases:
The Minor Planet Center
Orbit Database (MPCORB) is one of the most comprehensive catalogues.
Managed by the Minor Planet Center, it includes orbital elements and physical
properties for hundreds of thousands of known asteroids and other small bodies.
It is updated daily and is considered the authoritative source for asteroid
data globally.
NASA’s Jet Propulsion
Laboratory (JPL) maintains the Small-Body Database, which provides
highly detailed information on the orbital characteristics, ephemerides, and
close-approach parameters of small solar system bodies. It also has an orbit
viewer and links to different Application Programming Interfaces (APIs) for
those who want to work with the data.
NASA’s CNEOS Sentry
Database focuses on risk monitoring. It tracks potentially hazardous
asteroids (PHAs) and calculates their probabilities of impacting Earth over the
next 100 years.
Tracking asteroids
Once detected, an
approximate orbit of the asteroid can be calculated, using the diameter or the
absolute magnitude. However, this can change over months or years, as the mass
of the asteroid will depend on the composition, not the diameter.
In addition to the mass,
passing by celestial objects such as a planet, satellite or other asteroid will
change the orbit. The Yarkovsky effect – a force that acts on a rotating body
because of the non-uniform emission of thermal photons, is pronounced in
asteroids because of their small sizes, and can also play a part in changing
the orbit.
Hence, continuous and
precise tracking is a major facet of planetary defence.
In the future:
The upcoming NEO
Surveyor mission, scheduled for launch in 2027, is the first space
telescope to be launched to detect potentially hazardous asteroids by using
infrared space-based observations.
Asteroid Avoidance
DART (Double-Asteroid
Redirection Test)
On 26 September 2022, the
DART spacecraft collided with Dimorphos, a satellite of the asteroid Didymos.
It successfully shortened
the orbit of Dimorphis by 32 minutes, showing that it was possible to change
the orbit of a celestial body. Dimorphos has a diameter of 177m, and the
successful change in orbit showed that it is possible for us to deflect an
asteroid that might be on a collision course with Earth.
The change in orbit was
due to the transfer of momentum, mainly by the recoil of the debris that was
left by the impact more than the impact itself. DART took years to plan,
starting from the proposal to the launch. In case of an imminent impact, we
will still need months to build and launch the interceptor spacecraft. So,
detection and mitigation go hand in hand.
Some more ways to deflect
an asteroid
Gravity Tractor
A spacecraft hovers near
the asteroid, using its gravitational pull to gradually pull the asteroid off
course. It's a slow method but highly controlled and doesn't require contact
with the asteroid's surface.
Nuclear Detonation
A nuclear device is
detonated near or on the asteroid. A surface explosion could vaporize part of
the asteroid, creating thrust through ejecta. A subsurface explosion would
fragment it. This method is seen as a last resort due to political, legal, and
risk-related concerns.
Mass Drivers or Railguns
Mechanical devices mounted
on the asteroid eject mass from its surface, producing thrust over time. These
are still theoretical and would require anchoring to the asteroid.
Albedo Modification
The Albedo is a measure of
how reflective a celestial body is, which in turn will affect the Yarkovsky
effect. By coating the asteroid with materials that increase or decrease the
albedo, the Yarkovsky effect can be modified, changing the orbit.
Asteroid Approaches and
the Public
The Torino scale was first
adopted by the International Astronomical Union (IAU) in 1999. The Torino scale
assigns a number to potential impacts by mapping the size (and the kinetic
energy that will be released on impact) against the possibility of impact.
|
No Hazard |
0 |
The likelihood of a
collision is zero, or is so low as to be effectively zero. Also applies to
small objects such as meteors and bodies that burn up in the atmosphere as
well as infrequent meteorite falls that rarely cause damage. |
|
Normal |
1 |
A routine discovery
in which a pass near the Earth is predicted that poses no unusual level of
danger. Current calculations show the chance of collision is extremely
unlikely with no cause for public attention or public concern. New telescopic
observations very likely will lead to re-assignment to Level 0. |
|
Meriting Attention |
2 |
A discovery, which
may become routine with expanded searches, of an object making a somewhat
close but not highly unusual pass near the Earth. While meriting attention by
astronomers, there is no cause for public attention or public concern as an
actual collision is very unlikely. New telescopic observations very likely
will lead to re-assignment to Level 0. |
|
3 |
A close encounter,
meriting attention by astronomers. Current calculations give a 1% or greater
chance of collision capable of localized destruction. Most likely, new
telescopic observations will lead to re-assignment to Level 0. Attention by
public and by public officials is merited if the encounter is less than a
decade away. |
|
|
4 |
A close encounter,
meriting attention by astronomers. Current calculations give a 1% or greater
chance of collision capable of regional devastation. Most likely, new
telescopic observations will lead to re-assignment to Level 0. Attention by
public and by public officials is merited if the encounter is less than a
decade away. |
|
|
Threatening |
5 |
A close encounter
posing a serious, but still uncertain threat of regional devastation.
Critical attention by astronomers is needed to determine conclusively whether
or not a collision will occur. If the encounter is less than a decade away,
governmental contingency planning may be warranted. |
|
6 |
A close encounter by
a large object posing a serious but still uncertain threat of a global
catastrophe. Critical attention by astronomers is needed to determine
conclusively whether or not a collision will occur. If the encounter is less
than three decades away, governmental contingency planning may be warranted. |
|
|
7 |
A very close
encounter by a large object, which if occurring over the next century, poses
an unprecedented but still uncertain threat of a global catastrophe. For such
a threat, international contingency planning is warranted, especially to
determine urgently and conclusively whether or not a collision will occur. |
|
|
Certain Collisions |
8 |
A collision is
certain, capable of causing localized destruction for an impact over land or
possibly a tsunami if close offshore. Such events occur on average between
once per 50 years and once per several 1000 years. |
|
9 |
A collision is
certain, capable of causing unprecedented regional devastation for a land
impact or the threat of a major tsunami for an ocean impact. Such events
occur on average between once per 10,000 years and once per 100,000 years. |
|
|
10 |
A collision is
certain, capable of causing global climatic catastrophe that may threaten the
future of civilization as we know it, whether impacting land or ocean. Such
events occur on average once per 100,000 years, or less often. |
The objective of defining this scale was to give the public a familiar standard to interpret any announcements of an asteroids’ close approach. Just as the Richter scale is familiar to the public now, and a level 3 earthquake does not trigger mass panic, it was expected that an announcement of a Level 1 collision probability would be met with interest and not fear.
However, the fearmongering
does continue. It is important that most people are aware that they can check
the truth behind these announcements themselves.
Here is a guide for people
to interpret newspaper articles and videos, using the small body database.
A few successes of early
asteroid detection
2024 YR – the most recent
scare
Asteroid 2024 YR4 was
discovered on December 27, 2024, by the ATLAS survey in Río Hurtado, Chile.
Initial observations indicated a potential Earth impact on December 22, 2032.
On further observations, the probability of impact went up to 3.1% on February
18, 2025. This elevated its status to Level 3 on the Torino Scale, prompting
global planetary defence initiatives.
However, subsequent
observations led to a change in the calculated orbit, reducing the impact
probability to 0.004%. The Torino scale rating was brought to 0. However, there remains a 3.8% chance of 2024
YR4 impacting the Moon on December 22, 2032, which would offer a unique
opportunity for scientific observation of crater formation.
Apophis – the biggest
threat?
Asteroid 99942 Apophis was
discovered in 2004 and initially raised significant concern due to its
projected close approach to Earth on April 13, 2029. Early readings showed that
Apophis might go through a “gravitational keyhole” – a narrow region of space
near Earth. If it passed through, Earth’s gravity would have shifted its orbit
enough to set it on a collision course with Earth on the next approach (2036).
However, this possibility has now been ruled out.
But, the 2029 close orbit
of Apophis is going to be at a distance of just 32,000 km from Earth’s surface.
This will allow close observation of its orbital parameters.
What to look for in an article
Look for the number or name of the
asteroid – this is mentioned in every video clip or webpage.
Go to the Small Body Database of
NASA: https://ssd.jpl.nasa.gov/
This is a rich resource, but for a
quick check, all that is needed is to see how close the asteroid will actually
come to the surface of the Earth.
To do that, first enter the name or
the number of the asteroid into the search bar and press ‘ENTER’.
To get the details of the closest
approach, set the units to kilometres and click the up/down arrow icon in the
“Minimum Distance” column.
This will arrange the close
approaches in ascending order, with the closest approach listed first.
General observations
An asteroid impact is a definite
threat to the human species, but unlike the other species who have witnessed an
asteroid hitting the Earth, we have tools to observe and deflect an asteroid.
It is important that the public is aware of the risks as well as the tools
available.
Early detection is key in protecting
ourselves. In addition to the agencies which are at work detecting and
cataloguing, the public can also participate. I urge everyone to do their best
– whether it is informing your friends and family about the exact nature of a
news article, participating in an asteroid search or, if you are competent,
analyse the data available on your own.
This is for humanity – we need all hands-on
deck.
References
1. "Asteroid That May Be
Heading for the Earth Spotted by Astronomers." The Hindu, 25 Apr.
2025, www.thehindu.com/sci-tech/science/astronomers-spot-asteroid-that-may-be-heading-for-the-earth/article69183574.ece.
2. "Asteroid on Possible Collision Course
with Earth, Scientists Warn." BBC News, 25 Apr. 2025, www.bbc.com/news/articles/cqx9dgpx98go.
3. "Scientists
Discover an Asteroid Headed for Earth." YouTube, uploaded by
Territory, 25 Apr. 2025, www.youtube.com/watch?v=8hCbD2i72UM.
4. "2024 YR4 Risk
Corridor." Wikimedia Commons, uploaded 25 Apr. 2025,
upload.wikimedia.org/wikipedia/commons/8/8a/2024_YR4_risk_corridor.png.
5. NASA Center for Near Earth
Object Studies. “Close Approaches.” NASA, https://cneos.jpl.nasa.gov/ca/. Accessed 23 Apr. 2025.
6. Jet Propulsion Laboratory.
“New Map Shows Frequency of Small Asteroid Impacts, Provides Clues on Larger
Asteroid Population.” NASA, 22 Apr. 2014, https://www.jpl.nasa.gov/news/new-map-shows-frequency-of-small-asteroid-impacts-provides-clues-on-larger-asteroid-population/. Accessed 23 Apr. 2025.
7. "Meteors and
Meteorites: Facts." NASA, 25 Apr. 2025,
science.nasa.gov/solar-system/meteors-meteorites/facts/.
8. "Vredefort Impact
Structure." Wikipedia, Wikimedia Foundation, 25 Apr. 2025,
en.wikipedia.org/wiki/Vredefort_impact_structure.
9. NASA. “NEOWISE.” NASA
Science, https://science.nasa.gov/mission/neowise/. Accessed 23 Apr. 2025.
10.“Catalina Sky Survey.”
Wikipedia, Wikimedia Foundation, https://en.wikipedia.org/wiki/Catalina_Sky_Survey. Accessed 23 Apr. 2025.
11.“Pan-STARRS.” Wikipedia,
Wikimedia Foundation, https://en.wikipedia.org/wiki/Pan-STARRS. Accessed 23 Apr. 2025.
12.Minor Planet Center.
“MPCORB Database.” International Astronomical Union, https://www.minorplanetcenter.net/iau/MPCORB.html. Accessed 23 Apr. 2025.
13.NASA. “DART: Double
Asteroid Redirection Test.” NASA Science, https://science.nasa.gov/mission/dart/. Accessed 23 Apr. 2025.
14."Double Asteroid
Redirection Test (DART)." Johns Hopkins Applied Physics Laboratory, 25
Apr. 2025, dart.jhuapl.edu/Mission/index.php.
15.Betts, Bruce. “Asteroid
Deflection: Techniques to Save the Earth.” The Planetary Society, 1 Mar. 2023, https://www.planetary.org/articles/asteroid-deflection-techniques-to-save-the-earth. Accessed 23 Apr. 2025.
16.Rumpf, Clemens, and Hugh
G. Lewis. “Assessing the Impact Risk of Near-Earth Objects.” Acta Astronautica,
vol. 211, 2024, pp. 1–10. ScienceDirect, https://www.sciencedirect.com/science/article/abs/pii/S0094576523005593. Accessed 23 Apr. 2025.
17.Rumpf, Clemens, and Hugh
G. Lewis. “Probabilistic Impact Risk Assessment for Near-Earth Objects.” Acta
Astronautica, vol. 177, 2020, pp. 1–10. ScienceDirect, https://www.sciencedirect.com/science/article/abs/pii/S0094576520305634. Accessed 23 Apr. 2025.
18.NASA. “Asteroid 2024 YR4.”
NASA Science, https://science.nasa.gov/solar-system/asteroids/2024-yr4/. Accessed 23 Apr. 2025.
19.NASA. “Apophis.” NASA
Science, https://science.nasa.gov/solar-system/asteroids/apophis/. Accessed 23 Apr. 2025.
20.Thomson, Elizabeth A.
“Revised Asteroid Scale Aids Understanding of Impact Risk.” MIT News, 12 Apr.
2005, https://news.mit.edu/2005/torino. Accessed 23 Apr. 2025.
1 comment:
The article is so exhaustive and in depth, any one could understand so easily, thanks
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