cover of the November 21, 2020 issue

Lying low

During Africa’s dry season, when mosquitoes are scarce, malaria parasites in human blood turn their genes on and off to keep numbers low so infection doesn’t set off alarm bells for the immune system, Erin Garcia de Jesus reported in “How malaria parasites hide from the human immune system” (SN: 11/21/20, p. 8).

“How on Earth does the malaria parasite know it is the dry season from within the moist human body?” reader Elizabeth McDowell asked. “The human body must maintain moisture levels year-round.… What signals the parasite to alter gene activity?”

The mechanism remains unclear, Garcia de Jesus says, “but the researchers are searching for answers.” One hypothesis is that mosquito bites play a role. “Perhaps some protein in mosquito saliva tells the parasites, ‘Hello, I’m here to take you to your next victim,’ and the parasites adjust gene activity to ramp up their numbers,” she says.

E.T. phone home?

New methods are ramping up the search for alien intelligence, Maria Temming reported in “New search methods are ramping up the hunt for alien intelligence” (SN: 11/21/20, p. 18).

Many readers were intrigued. The story “challenged my memory on the search for messages from aliens with [Temming’s] statement: ‘So far, SETI scientists haven’t picked up a single alien signal,’ ” reader David Cosson wrote. “My recollection was that NASA launched the two Voyager spacecraft in 1977 each carrying a golden record that included 90 minutes of world music, including Bach, Mozart and Chuck Berry’s ‘Johnny B. Goode.’ I thought I recalled a press report … that NASA had received a reply from aliens who had played the record. The message was: ‘Send more Chuck Berry.’ Perhaps my memory is faulty, but I recall the reporter as somebody named Steve Martin,” Cosson joked.

Reader Bob Johnson remains puzzled by some researchers’ efforts to detect radio frequency signals. “It is highly unlikely other civilizations are, like us, going through the first 100 years of communication evolution,” Johnson wrote. “We should be hunting for signals in the ultraviolet, X-ray and gamma-ray frequencies. Even though older technologies work, they are displaced by new methods. Looking for [radio frequency] signals from E.T. is analogous to listening for … modem tones as an indication of intelligent life.”

Watery skies

Water high up in Mars’ atmosphere splits apart within a few hours, leaving hydrogen atoms to float away, Lisa Grossman reported in “Chemical reactions high in Mars’ atmosphere rip apart water molecules” (SN: 12/5/20, p. 14).

Reader Lorenza Zamarron wondered what happens to oxygen. “Where does the oxygen go? If the oxygen is heavier, does it fall back down to Mars? Is it destroyed?”

At least some oxygen breaks free of Mars’ gravity in a process called photochemical escape, says Shane Stone, a planetary chemist at the University of Arizona in Tucson. “Additionally, some oxygen would inevitably be transported down toward and around the planet,” Stone says. “Many scientists believed that atmospheric chemistry would, over very long time periods, balance the escape of hydrogen and oxygen to match the 2:1 ratio that these elements are found in water. However, some of us are rethinking this concept in light of this discovery of water transport directly to the upper atmosphere,” Stone says. That oxygen is slow to escape could partly explain why the Red Planet is red. “Oxygen in the atmosphere reacts with minerals on the surface to produce iron oxide (rust), which is responsible for the reddish-orange color that is so indelibly Martian,” Stone says. “In other words, Mars is oxidized.”

Correction

In “Meet 5 Black researchers fighting for diversity and equity in science” (SN: 12/19/20 & 1/2/21, p. 26), the name of a BlackAFinSTEM group member was incomplete. Her name is Anna Gifty Opoku-Agyeman.

Stay tuned

In 1970, researchers thought Earth’s magnetic pole reversals might be to blame for long-ago extinctions of single-celled organisms called Radiolaria (10 living species shown below). But no strong evidence of a direct link has turned up, Jonathan Lambert reported (SN: 11/21/20, p. 4) in an update to the article “Effects of Earth’s magnetic field” (SN: 11/21/70, p. 392). Reader Doug Pruner joked: “Radiolarian extinctions? Of course. The reversals caused interference with their radios.”